I'd be very surprised if Musharraf had a direct role in the killing. I think, on balance, he stands to lose more now than before.
Brett
As usual, Brett is one of the more rational ones here. Shocking......
Bhutto was not that popular in Pakistan, her rule was known as particularly corrupt in a country that is used to it. While the international media has depicted widespread chaos in parts of the country in the past, like when Musharraf declared emergencey rule, the reality was quite different on the ground. I don't know if that is the case this time but I would imagine that with her relatively little support she had among the public, whatever rioting there is will die down soon.
The people in Pakistan aren't particularly fond of Musharraf but none fo the alternatives, including Sharif, Bhutto (formerly) or the fundamentalists, are particularly appealing. Where the fundamentalists did make gains in elections a few years ago in the Northwest Frontier Provinces that border Afghanistan(Google it, it is among the most lawless parts of the country, and where Al Qaeda and the Taliban have a large amount of support), they are in danger of losing a lot of power in the next election because they failed to deliver on basic promises like better sewage and water services, simple bread and butter issues. They failed where governments before them failed and will probably pay for it at the ballot box (ironically, that is large part of the reason why Hamas and Hezbollah gained a lot of support in Palestine and Lebanon, they provided services when Fatah and/or the government could or did not).
I don't see Pakistan slding towards a civil war quite yet. Part of the reason we are seeing a lot of violence in Pakistan right now is a simple matter, we are paying more attention to it nowadays. It has long been a chaotic and violent country. Bhutto's father was executed and the President who was responsible for it, General Muhammad Zia-ul-Haq, died in suspicious plane crash in 1988. There is a lot of turmoil and violence over there right now, but the Army still holds the keys to power and they don't like the fundamentalists and they don't wnat their nukes to fall into the wrong hands. And most of the public sees the Army and its leadership as the only halfway competent authority in the country.
So as long as the Army and the people are okay with the Army, Pakistan and its nukes will be somewhat okay, whatever okay is in that region of the world.