Is Billy the Final Cylon?

For a long time now I've ranked Billy as my top choice for the Final Cylon on Battlestar Galactica on the grounds that it would be the writers' only chance to rectify what was surely one of their worst-handled plotlines. Now I see that Ron Moore recently approached actor Paul Campbell about reprising his role as Billy—not as the final Cylon but rather as a dream figure in Roslin's subconscious (a bit from the penultimate episode of the season which ultimately went to Elosha). If the info on io9 is accurate, it seems pretty likely that Billy isn't the Final Cylon, which means I'm now laying all my chits on Cally.

And while we're on the subject, Jane Espenson should really try keeping this under her hat:

When Campbell's lack of availability changed that plan, writer Jane Espenson detailed the amount of work that created to fix the script:

In a hallmark of what I consider really fine writing, I just did a global search and replace on the name. I did not change the lines. The only thing I did... I added 'Cue the celestial trumpets.' That one phrase that Elosha has was all I did to change it.

As Moore says in response, "There you go. That's how finely detailed this stuff is."

It's further worth noting that of course the actual identity of the Final Cylon really doesn't matter in any thematic sense, and indeed the revelation probably won't make any narrative sense at all. But I find it to be a really intriguing problem of television production—after years of build-up, and especially after last year's four-for-one season finale, how could this last plot twist ever be remotely satisfying? I must admit I'm fascinated by the problem the BSG writers have created for themselves, and I'm quite interested to see how they decide to try and solve it.