In an intriguing essay, Michael Hall of Galactica Science pieced together Head Six's and Head Baltar's full final lines of dialog by combining what we saw in the episode itself, and adding in what is read from the script in the final cast read-through as shown on Sci-Fi.Com and Hulu. Additional lines are in italics.:
Head Six: Commercialism, decadence, technology run amok. Remind you of anything?
Head Baltar: Take your pick. Kobol, Earth - the real Earth, before this one, Caprica before the fall.
Head Six: All of this has happened before.
Head Baltar: But the question remains, “Does all of this have to happen again?”
Head Six: This time I bet no.
Head Baltar: You know, I’ve never known you to play the optimist. Why the sudden change of heart?
Head Six: Mathematics. Law of averages. Let a complex system repeat itself long enough and eventually something surprising might occur. That too is in God’s Plan.
Head Baltar (whispering/growling): You know it doesn’t like that name! In any case, it would have required mankind in all its flaws to have learned from its mistakes.
Head Six: Stranger things have happened.
Head Baltar: I think I’ll take that bet. What are the stakes?
Head Six: Hmph. (Head Six gives a look of annoyance.)
Head Baltar: Silly me! Silly, silly me!
It's interesting that they decided to cut out their wager. The wager almost makes the Six and Baltar apparitions to be like mischievous spirits, or something akin to Loki.
Perhaps the full scene will end up in the longer version of Daybreak on the DVD. In any case, the "Silly me," bit actually makes more sense in that full context of Six apparently being disenchanted with Baltar's proposal for a wager on the fate of humanity...