The Kara that came back from Earth isn't a human or a cylon - and it's probably something to do with whatever they harvested from her womb on that Farm.
The final five, along with the other skinjobs from Earth are possibly really hybrids? Besides the fact that in that flashback, there seemed to be a population teeming with unique individuals that age like us, the Chief was wearing glasses. Why the frak would a cylon need to wear glasses? Also, this is how the Six could get impregnated by Tigh. And if they're not part human, then they're still clearly a different kind of cylon that is physiologically more like humans at least... If Hera is the shape of things to come, it'd follow that the population of Earth before it was nuked could be where the fleet is eventually headed as more of them interbreed, before the whole cycle eventually starts to repeat itself again.
There are 13 models. Thirteen colonies = thirteen models. My money's on Dee - probably wouldn't have necessarily bought into that speculation if not for the fact that a) she was positioned with Hera right before offing herself and b) Anastasia = resurrection. The Six on the Pegasus also took a name meaning resurrection. Either that, or it's one hell of a red herring.
As for the whole Ellen/Six connection thing.. it does sort of make sense, but I have no idea where, if anywhere, they may be going with that. It is kind of interesting to note that the Sixes don't have any sort of unified name that they tend to go by. Like, in this rebel faction, we've got the Sharons and Leobens.. and the Sixes. Hmmm.
Heh. Just watch me look back at this after the finale and feel like a retard.