Of course, the main question behind all this is: Who's the last cylon? There's also the question of: Is there one more cylon, or two?
I think, or rather, I hope, that it hinges on how the thing with the Lords of Kobol worked way back when, with the twelve gods and the cylon god. It's not clear if the one god who wanted to be worshiped above the others is the cylon god or not, but it would be very nice if, regardless, that god were a thirteenth god outside of the twelve that are still worshiped. That would,
as I said way back when after watching the first season, correspond nicely to the thirteenth colony. I think it's interesting that we are no further along at all to knowing what the hell's up with all that than we were back at the end of season one.
Certainly the number of cylons total should match the number of Lords of Kobol plus their own god (I think). If their god was one of those Lords, just the twelve, then it seems quite plausible that, as
jennyo is fond of surmising, the twelfth cylon should be the cylon god (whether or not that cylon is Roslin or not). If their god was either a thirteenth Lord of Kobol or wasn't one of them at all, then I think there should be a thirteenth cylon model waiting in the wings. The Temple of the Five on the Algae planet is supposed to refer to five priests who worship "The One Whose Name Cannot Be Spoken." For now I'll just call him Lord Voldemort.
-- But oh my god, I think I just (maybe) figured something out - there's not a thirteenth cylon model, nor is even the twelfth model the cylon god. Instead, Baltar (with his new Cult of Baltar and his perpetual and total focus on mememememe) is the recurrence of the Jealous God, and/or the recurrence of the Cylon God. There's that group of people worshipping him, as opposed to when they worshipped Roslin as a prophet of the twelve gods, and he just fits all the necessary particulars of that character. Especially with the Hybrid and also phantom!Six calling him the Chosen One... --
Back to our regularly scheduled programming, though, Lord Voldemort seems likely to be the Lord of Kobol who wanted to be worshiped as the only god, hence his name needing to be obliterated. And if there were five priests who served him particularly who were on the way to Earth, then it seems that Lord V. should be associated with the twelve gods in much the same way that the thirteenth colony is associated with the twelve colonies. In other words, as a thirteenth. Maybe Roslin's the twelfth cylon, but that doesn't stop Baltar from being the thirteenth, jealous one, whether or not he himself is a cylon. (And it's true that he doesn't seem to be, by this point.)
I'm probably done wittering on that topic for now, but here's another (related) topic to chew on:
There have been three named places or artifacts - the Arrow of Apollo, the Tomb of Athena, and the Gates of Hera. These are the only three names used for actual people on Galactica. The Arrow of Apollo was the clue to Earth's location, and currently the "arrow" (viper) of Apollo could be said to be leading the colonists to Earth (although he himself is evidently following Kara). And the Gates of Hera were closely linked with the death of Athena - she died jumping from those mountains in grief. Caprica-Sharon, later dubbed Athena, is also essentially the one who leads the landing party to the Tomb of Athena, though the question of whether RM already planned to call her Athena at that point is totally up in the air. (Or maybe it's not up in the air, but I don't have the answer.) Really, it's just a pity that Lee can't be a cylon! (Though I suppose, really, who knows, what with this whole new set of breaking-the-rules cylons, but it still seems highly unlikely.) But I wish that he were just so that there could be an even nicer correspondence between the twelve Lords of Kobol and our twelve cylon models. Not that Hera's one of the twelve, of course, but still.
My biggest question, though? What ever happened to Boxey? ;)