Boone.
The end.
Okay, I'm kidding. I don't want Boone to die. I shall be angry if Boone dies. Why? Because I think he's a really great character with amazing depth and blahblahblah? Nope. I just think he's a cop-out. And I think that, with a bit more time, Boone could be pretty decent character. As I've said before, he's just in his clumsy-puppy!stage. You know the type, that stray puppy you find when you're out playing and they won't stop following you and they're so cute and trip all over themselves and aren't exactly bright but endaering anyway? Yeah, he's in that stage. But, apparently, he also seems to be that puppy that gets run over by the car because he's so excited and just wanted to play with everyone and follows his master across the street but doesn't look both ways.
But, for the sake of it not being Boone (a poorly aimed shot in the dark), I shall theorize about other people dying.
Josh Holloway (in TV Guide) says that it's someone whose storylines haven't been developing, and he also states that the person is a good friend of his. I don't really know about Ian's buddybuddy tendencies with the cast, so I can't say anything about that. I do know that Naveen and Josh are pretty friendly, as are Josh and Harold.
So, as you can tell, I'm banking on the non-Boone person being either Sayid or Michael. For the following reasons:
Locke is indirectly responsible for the death of the character, but not in the way we think. Okay, so I think Locke is indirectly responsible for Boone's death by getting him to climb up into that plane. So, assuming everyone else thinks that as well...well, that wouldn't be it, would it? But then, Kristen is a liar. So who knows.
Also; Walt knows more than he should. She explains this directly after spoilery stuff concerning the death, so if this is added in, unless Walt is incredibly sneakysneaky and junglesavvy, or he's been swapping secrets with polar bears, there's no way he could know more than he should concerning the Locke/Boone incident. I would be very disappointed in the show if he somehow ended up following them or something ridiculous like that. He's 10. Creepy powers aside...he's still TEN. And it's a big jungle. Yeah.
Also, it's JACK that sets out to kill someone, not Sayid. So sayeth Kristen recently. Again, she's slightly a liar, so take that with a pound of salt.
The person's storylines haven't been developing. This, again, leaves us with Sayid, Michael, and Boone.
So, assuming all of this and applying it to Michael:
Locke hasn't told anyone about Walt's destructive tendencies. This could end up being to Michael's demise. Also, it's said somewhere that a main lostaway kills another lostaway, so that could play in to Walt someone killing Michael (accidentally, of course. Walt isn't a crazeh.) Locke also hasn't told anyone about the 'monster' and Michael, as uptight as he is, would definitely have a problem accepting whatever the monster has to offer. Boone needed aide in accepting it, and, perhaps when Michael comes face-to-face with the monster, he just fails. *shrugs*
Walt knows more than he should. Walt burnt down the raft, and obviously has access to pyrotechnic-friendly supplies. He knows how to throw knives around like Locke, and who knows what else Locke passed on to the bratty padawan. Walt may also have figured out the Island's secret by now, he's been quite absent lately.
Jack's out to kill someone. Jack could find out that Locke lied, and set out of kill him. Michael would be one of the very first to hop on the 'Slay Locke' bandwagon, and seeing as we all know Jack and Locke aren't dying any time soon, Michael would naturally be the one to be offed in that scenario.
Michael's storyline hasn't been developing a whole lot. True, he has the doomed HMS Flammable, but that isn't really a progressing storyline by means of character development. I suppose his budding friendship with Jin could count, not to mention, we now know what exactly happened with Walt. But Michael's character development, much like his raft...isn't really going anywhere.
Now, applying it to Sayid:
Locke will be indirectly responsible because Sayid will also leave out on the 'Slay Locke' bandwagon. If nothing more than to make Shannon feel better because her sex-slave brother is dying. Really, at this point, Locke's lying about the plane and lying about the 'monster' could play into anyone's death, because they're both big points.
Walt knows more than he should. This could just be Walt being nosey and snooping through Sayid's things and finding something. Again, I don't know how much, if at all, Walt's omnicence actually plays into the death. So anything concerning Walt could be removed from all of this.
Sayid's storyline hasn't developed since he left Rousseau. And, before you all jump on me with 'omgwtfShayid!', I'm including that. The whole Shayid thing is more of a step for Shannon, not Sayid. He's been in wuv before and this isn't the first time for him for any of that. Just because he hooked up with Shannon doesn't mean his character has developed, it just means his character is getting some action. Shayid is a development of Shannon's character, which was made obvious with her conversation with Locke. It's been about Shannon, and slightly about Boone, not really about Sayid. Sayid is also very well-featured. His storyline hasn't really progressed, because all he's been doing is attempting to translate Rousseau's stuff, and really, he hasn't been doing it. Charlie made the Black Rock connection, Shannon translated the French, Hurley noticed the numbers, Locke provided the compass....so...yeah. Sayid is also 'kind of sexy' as Kristen said the walking!dead lostaway is. Naveen also has projects lined up and whatnot outside of LOST. I know 'Bride and Prejudice' has premiered some places, but that could be considered, and he may be lined up for other things. *shrugs*
Why it shouldn't be Boone:
Boone isn't really well-featured. Boone, despite his uselessness, has a (very) slowly developing storyline. He's become Locke's padawan, he's moving towards getting over Shannon and getting past seeking attention and all that snotty rich-boy jazz he comes with. While his flashback was slightly pointless other than to give an insight into Shannon's shallow nature and Boone's slightly twisted needy one, it isn't the first useless flashback. Kate's entire bank scene flashback was useless, really. We only needed one, and really, we didn't need it, she could have just said, 'I have a toy plane that a man I loved had' It wasn't worthy of a flashback, same as the Shaboone past might not have been. And, I suppose, if you look at it, Boone's flashback wasn't worthless, it did help you realize that Boone has done nothing but take care of Shannon since they were pushed together into sibling-ville. Even if it was only because of his 'crush' on her, it just shows Boone has a weakness for helping people, and even for being dominated. He has a hard time being his own person, obviously. *shrugs* Yeah, I'm totally reaching the dark here, because I didn't start liking Boone until last week.
Also, Locke has said more than once that Boone's destiny, as well as his, was the find what's in the hatch, to find out what the island wants and what the island...IS, essentially. I think he even mentioned in one episode that Boone would live to see it, or something of that nature. Locke is creepy, so who knows. I had loads of other little things that could have made it as though Boone was meant to live, but I've forgotten them all.
Why it will be Boone:
There's really no way he could survive, if you look at it. Jack's track record is absymal so far, and he's a spinal surgeon, which means he's out of his element in nearly everything he's going to try and do on this island. Boone probably has loads of broken bones, possibly punctured lungs, ruptured who-knows-what-else, and we won't even touch on his external wounds. Jack would have to pull out some miracle nonsense and bring Sun in with her magical Asian healing techniques as well. And even then, Locke would need to do some witchy man hoodoo, and we all know he's gone for a while. Realistically, Boone would die.
The previews practically spell it out for you. Jack has Luke-Skywalker'd Boone into death, anyway. You never tell someone that everything's okay, they aren't going to die, and you won't let them give up. Honestly. I'll bet someone told Boone the Force would be with him before he boarded that plane too. Poor guy.
Boone was carrying around the red shirt when they first started searching for Chaire, and he foreshadowed his own death with the Trekkie reference.
Locke is completely and irrefutably indirectly responsible for Boone's death. There's really no way around that.
Boone isn't too keen on staying alive anyway, if the previews aren't lying (which we know they're quite prone to doing)
So, who I think will die: Boone
If not Boone; who I think will die, in order of likelihood: Sayid, Michael
If it's anyone other than that...I'll probably die. Also, you'll note my rage is Boone dies, simply because it's a copout. Like Kate having to deliver Claire's baby. And don't EVEN get me started on that. *grumble*