The PPP and PML-N have formed a coalition government, and they have almost 2/3 of the seats in Parliament.

In order to change the constitution, they would need a 2/3 majority, with impeachment requiring the same numbers, but their current majority appears to be enough to reinstate judges.

I don’t think that Musharraf is long to his post as president, and in fact, if the judges are reinstated, they may rule his last election to that post to be illegal.