I think that there might be another captive Queen Alien on board, with an egg sack and see lays a couple of eggs which attach to other Preds and make more Predaliens. (scary but it could happen) then with all of the hybrids running around the ship's mainframe control system crashes causing it to fall back to Earth in the small Colorado town. the hybrids escape as well as Queen who lays more eggs in town and normal looking (non hybrid) Aliens are born. Second thought is the one Predalien sneaks to the controll system and destroys it basically doing what I said above, except there are no more Predaliens and there is still a captive Queen on board who lays eggs when she escapes in Colorado town and normal Aliens are born from humans. Personally I think the first one is correct because someone from the AvP 2 movie production team stated that there could possibly be more than one hybrid. Also the fact that there is only suppose to be mainly one Pred, if the many hybrids don't go around killing like I stated in second idea then some Preds would have survived the crash. But with many Predaliens all Predators would most likley (sadly including the Elder, not Wolf) die.