So what are Head-Six and Head-Baltar? I have read a few vague suggests that they were agents from the future, but i was hoping to find out how other people interpreted the scenes. I was under the impression that they were some type of transmission from the future. Basically, I'm leaning towards the idea that Baltar and Caprica survive for 150,000 years and ultimately send messages back to themselves paving the way for humanity's.
I believe this because Baltar has had this uncanny instinct for survival from the start. I honestly don't think it's far fetched that he could find a way to survive for another 150.000 years with Six. Even though he doesn't have the tech, it always possible that the Centurions come back. And with Baltar's technological no how, kazaam!
It would be a great way to explain where all the prophetic visions were coming from. It could also explain why so many integral characters managed to escape the holocaust in the 12 colonies. (For example, all 5 final cylons survive. )
I also believe this because in past episodes, when Baltar was on Kobol, Head-Six told him how they would have children. To me Sol-Earth's (as in sol = the Sun) humanity is Baltar's and Caprica's children.
There are other possible explainations, but that's my favorite possible explaination.