Okay, I've now seen like... 5 episodes in total.
Starbuck is so obviously the 5th Cylon. I mean, duh.
Edited. My theory now under the cut - may contain spoilers of the most recent episode.
Okay, so my theory is that there are WAY more Cylons out there. I mean, if Earth was full of Cylons, and our hidden Cylons were among them, as well as that one dude's wife (who he's sure reincarnated), then why wouldn't all of the others reincarnate? They would. And they're all living on some safe and habitable planet, which the BSG team will find in or near the last episode, and all will live happily ever after in sweet harmony.
And Starbuck is a Cylon. As are many of the people who believe themselves to be human, most likely.
XD I can't believe I've only seen like... 6 or 7 episodes and I'm already forming grand theories.
Also, honestly, I don't really like the series. I know many of you will find this to be horrible blasphemy, but I just don't really care for it. Watching these episodes has made me pretty sure that the last few seasons have been very slow moving (given that these ones were slow moving and they seem like they're supposed to be fairly climactic), and I have yet to form an emotional bond with any of the characters which likely means that I never will. The characters mostly just annoy me with their bad decisions and alcoholism. Also, the filming style annoys the fuck out of me. It looks like it's filmed by a complete amateur with a camcorder - all the sudden, jerky zooms and turns and the constant shaking.