Well, it seems the "13th tribe" that inhabited Earth destroyed themselves. The BSG gang and the remaining Cylons showed up - and all life was gone. The question now is: Where to go from here? Given the considerable "background radiation" detected, it does NOT seem Earth is inhabitable. Do they go back to New Caprica or do they keep searching for another planet that can support life? Can human and Cylons NOW co-exist in peace? Things that make you go "Hmmmmm......"
Anyways, I don't think that was earth at all. In the end of season 3, they viewed out and then zoomed in and you could see the United States. In the last episode, they didn't show anything that looked like Earth. I think it is a trick because like you said before, this might be a fake Cylon Civil war.
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