I haven't frequented Battlestar Galactica discussion boards, so I don't know what popular theories are out there, but this is my prediction (or at least, this is what I'd like to see). It looks like a lot of answers may be given in next week's episode, so I had better put my theories out now, to be confirmed or exploded (which is more likely) as the case may be. I may also be repeating elements of speculation that people have already put out there -- I don't know.
These theories contain spoilers up to and including last week's episode
Blood On the Scales, so if you are not caught up with current Battlestar Galactica episodes, and do not wish to be spoiled, then I recommend that you don't read this! The rest of it is my own speculation and does not come from any super-secret link to the production team, etc. etc.
( My theory of how Battlestar Galactica will end or... what is the grand meaning behind it all? )