Mush needs "an offer he can't refuse".
It's just a matter of time before he's gone anyway. Bush won't do anything to make his life more difficult because he doesn't want to demonstrate ingratitude for the help he's given. But the minute Musharraf is gone, our policy is going to change with respect to Pakistan.
heck, the muslim extremists have been trying to give him one for some time now. It is amazing he is still alive.
If he goes, whoever takes his place is going to be far less pro-US. Like the Saudi royal family, he is far better for us than what would replace them. Given those options, it makes no sense at all to act against him. It isn't like the covert assistance he surely gives the US makes front pages or anything, he cannot afford for it to.
The bush administration understands this, clearly.