Cally Tyrol is the fifth and final Cylon.
There. I said it. The gauntlet is thrown. What’re ya gonna do? Nothin. Deal with it.
Check out this “Last Cylon Supper” pic and blurb from io9.com (Gawker’s new scifi blog). I wonder if they served toast. I read the clues from Ron D. Moore and I’ve interpreted them thusly: The final-fifth is NOT in that photo (Cally is NOT in that photo), and he refers to Cally and Chief Tyrol’s baby as “seeming to be the 2nd human Cylon hybrid.” There’s your money shot. He SEEMS to be but he’s not. He’s the first biological Cylon baby.
Season four won’t premier until April so we probably won’t get confirmation on this for quite some time. Go ahead, and place your bets in the comments. I’m sticking with my theory (at least until it’s proven completely and utterly wrong).