Short-term:
Democrats become conservative and Republicans become liberal. Don't ask how this happens.
Long-term:
Racial polarization continues on track as Minorities populate the sun belt and Whites sharply trend R regardless of regional cultures. Somehow, CA loses its high Asian/Hispanic population to the southern states or Hispanics in CA start voting like Cubans for whatever reason.
I guess... Won't happen as far as I see. The Republican party will eventually have to become more inclusive or lose its national status.