Been thinking about Reichenbach, and how everyone keeps saying Martin Freeman will utterly break our hearts in it.
So John sees Sherlock fall. Or maybe he doesn't. Either way, he sees Sherlock injured, and claws his way through a crowd to try and help him. Only Mycroft's men (or the paramedics) keep him back. Of course they do: probably because Sherlock isn't really dead and John needs to think that he is. But I'm banking on an additional 'insult to injury' moment where someone - Mycroft, probably - reminds John that although he may be a doctor, he is no longer a qualified trauma surgeon: a bullet in Afghanistan saw to that.
"You can't help him, Doctor Watson. Leave him to those who can."
So John is left standing alone, helpless, unable to save his friend.
For this moment alone - if it happens - Sherlock will deserve that mighty roundhouse to the jaw that all of fandom wants John to give him when he comes back.
EDIT: Possible alternative ending: they've certainly set up the possibility for Sherlock faking his own death in Scandal and Hounds - we've seen that even Mycroft's experts can misidentify a corpse by cleverly faked DNA, and certain drugs can make people see what they expect to see rather than what's there (like, perhaps, someone mortally injured after falling off a building).
But what if, instead of "killing" Sherlock off, the writers decide to end s2 with him injured and in a coma, with possible brain damage from the fall? That would certainly flummox the hardcore Sherlockians who thought they knew how this story ended, plus add a very real uncertainty to s3...can Sherlock really come back from this Fall? Will he still be the same supergenius as before...and if not, what then?
(Also, it'd be a great opportunity to work in some themes from "The Adventure of the Dying Detective", one of my very favourite canon stories...only Sherlock could be faking brain damage instead of a tropical illness, and tricking John into believing he was really impaired, all for the sake of a case. John might even struggle with whether or not to have Sherlock sectioned before the truth finally comes out. Lovely, tasty angst; nummy nummy.) :)
EDIT THE SECONDE: Also also, my prediction for when Sherlock does come back, if they stick to the "faking his own death" scenario:
SHERLOCK: Ta-da! Hello John, it's me, hooray!
JOHN: *punch inna face*
SHERLOCK: Ow!
JOHN'S NEW WIFE: Ooh. Hello there. Who's the funny man on the floor, darling?
Because if they're going to introduce a Mrs. Watson, as Moffat keeps threatening to do, then that would really be the most logical time and place to do it. And, to my mind, an even better comeuppance for Sherlock than getting punched in the face...can you imagine the epic sulk? "Mycroft, why didn't you TELL me?? Him being grief-stricken I could have dealt with, or even morbidly depressed; but MARRIED?? This is intolerable!!"
Q