If Mubarak goes there are 3 ways it could go:
FreeFor: People who are protesting who wish a better life for themselves.
China/Russia: The great agitators. Count on them doing anything that is bad for the US. And they have the resources to keep this going to vested (I won't use "OUR" in this post) interests detriment.
Islamists: Iran and friends, they have a way of working their ways into the FreeFor. And this is potentially the biggest coup for them.
Obviously vested interests in DC and NY want Mubarak because the devil that we can control via foreign aid is better than any other unknown devil.
The problem lies in who "gets" Egypt. If the wrong people do, which I would say is 80/20 for, count on Jordan falling (catastrophic) and then Saudi Arabia and the rest of the "stable" countries in that part of the world.
And if Islamists get Egypt (Hezbollah) buy stock in whatever company supplies the rocket fuel to Israel's nuclear program.