I think the final cylon may well be Dualla - she is technically an 'Adama' by marriage to Lee (Leoban told Roslin the cylon is Adama), Dualla's first name means resurrection (Anastasia), and if you look back to certain episides early on you can see by here reactions to certain events that she may be hiding something (eg her reaction when the listening device is found in the CIC, listening in on conversations in S2 between Lee and Starbuck) - and as Ron Moore keeps on saying it's not Roslin, Bill or Starbuck it most likely has to be Dualla or Gaeta (can't be Helo - he's the father of the 1st human-cylon child - and everyone else is already a cylon
), so I'll go with Dualla.(and am prepared to eat humble pie when the final cylon is exposed
)