My only real disappointment is that there wasn't a ruined Statue of Liberty sticking out of the ground.
Anyways, I guess the story options here are:
A: There's another final planet to find; perhaps where this Earth's inhabitants have escaped to...
B: Introduce some dues ex machina using time-travel/alternate dimensions/spiritual hocus pocus/reboot...whatever.
C: Send them back out into space without a sure destination, either in conflict or partnership with the Cylons.
Anyone else?