It would slowly evolve into something different but that would take a while to happen. I agree that the GOP dying, really either party dying is kind of an absurd premise but I don't think that its entirely outside the realm of possibility that for the short term at least at the Presidential level the GOP may be facing an uphill battle.
I definitely agree that it is evolving. That is why I think Paul has a distinct edge. Like Clinton before him, he is offering an evolution to revive a dying brand.