I remember my IR professor telling us that Pakistan was one assassination away from being an extremist Islamic state with nuclear weapons. Here's hoping this wasn't that assassination.
Your IR professor is and was very wrong.

Many key players and how they react will be tested here. How does Musharraf react, and are elections postponed? How does the PPP reorganize itself and who will be its new leader with no clear Bhutto clan figure ready to take the reins? Will the PPP blame Musharraf and the military?

If it comes down to a real confrontation between an enraged PPP and the military, things could get very messy. But I think in the long run that the PPP will end up breaking apart much as the PML has done, with a significant wing coopted by the military.