I am sure that during 1st BSG season None either of us or even more of the writers of BSG had in mind THE FIVE FINAL CYLON/PRIEST concept that actually unifies Cylon/human history. Just don't forget this as we refer to five persons honoured by both Cylon and Human history. Anyway At 1st season suggesting that either Tigh or Tyrol were Cylons would make many of us turn off their TV sets.....
They must have conceived this idea after the end of Season 2 and only after they reached a general conclusion on how to end the BSG series! My opinion is that Moore will end BSG quest with many surprises one of which would be the revealing of the Final Cylon/Priest: My idea is that the final one is to be of greater importance than the rest revealed....
Ok BSG is a TV series and not a historical event, The writer needs drama and the final Cylon/Priest must be higher in rank than Tigh... otherwise he would reveal Tigh LAST.... So it is Roslin, Adama, Starbuck or Baltar.... Roslin, Baltar and Adama have more than 100 clues pointing them as Cylon/Priest each one actually due to the fact that they are the leading actors of the show. Although Moore has stated that the final five is not present in the Supper photo I don't believe him... on contrary I strongly believe him in telling that this will be the final season for BSG as he opposes to the idea of leaving the show half ended in case SciFi fails to order a 5th season (5 years is already remarkable achievment for a Sci-Fi remake film..)
Of course writers can improvise and provide us as a flashback clues to support their final choice. They could actually provide clues that even.... Romo's cat is the final Cylon-cat.... if they wanted to do so...Don't forget that BSG has a clever scenario. They forwarded season 3 timeline leaving unfilmed one whole year of New Caprica settlement just in favour of the writers to improvise anything that they may think of later... We saw as a flashback Lee's and Starback's marriages, we suddenly saw Tyrol together with Cally being pregnant and many more...
Brad's idea of Joseph Adama being a cylon would spoil the Caprica Series if they ever surface on TV...
I strongly believe that this BSG will end in a completely different way than that of the 1980 series. Simply finding Earth will just be a poor scenario for Moore that introduced SO MANY CHANGES IN THE BSG-2003 series making it a completely NEW Serial rather than a remake of old 1977-1980 BSG that I used to watch as a child. He will definitely go with a BANG most probably with a time loop scenario!
The FIVE FINAL CYLON/PRIEST theory actually presents a deliberate (writer implemented)time discrepancy as the 13 tribe 4000 years ago build a temple honouring five entities that were also not only honoured by the Cylons but were actually recognised as the five final of them (Cylons didn't exist at that time... or maybe they did....!!!!!!!) In the script the whole idea is obfuscated as the rest of the Cylons are prohibited to speak freely about the Final Five (with the exception of De Anna that seeks them) and Baltar who although being the only human aware of the fact that the FINAL FIVE CYLONS & FIVE HUMAN PRIESTS are common entities he fails to bring it to attention to the rest of the fleet when he returns to Galactica. In case you forgot a few hours previously he had made clear to the Cylons that the Cylon-Human converging over the Algae planet a few hours before a star exploding was MORE than simple coincidence..
Just to end this comment I believe that Moore will bring the scenario upside down: Most probably life started at Earth...the real journey was an exodus from Earth to Cobol... and yes Cylons existed right from the start and Galactica with humans together with Cylons are coming back either to future earth to find out their common origin and heritage or to past earth to correct the time glitch (Starbuck's wormhole travel to earth PURSUING A CYLON RAIDER THAT most probably crashed on earth..) that led to Cylon creation right from the first time...