I think that if AJ doesn't prove to be the long term answer this season, one of two things will happen:
1. the Dolphins draft a QB in the first round next year, and let somebody (maybe somebody already on the roster, maybe a veteran like Jon Kitna) play "caretaker" until the young guy develops.
or
2. The 'Phins trade for a (relatively) young QB with serious upside. Maybe one of the San Diego QB's, or some other youngster sitting on the bench somewhere. Would Schaub be one of those candidates? I don't know, I haven't seen enough of him to even have an opinion on the guy myself.
I think (1) above is more likely though. Saban has already spoke about how he believes in building through the draft.