Zardari had announced earlier that he wasn't going either, so it only follows that Musharraf took the safe side and decided to stay in Pakistan to assess the situation.
I doubt we will see either resignation or using Article 58(2b) to dismiss the assemblies. Dismissing the assemblies would not only dive the country into a very serious political strife, but the newly elected assemblies after elections would almost certainly be chock full of PML-N and allied APDM parties who would be openly hostile and certainly impeach him, as well push through constitutional reforms to repeal the 17th Amendment, restore judges, etc.
Now, as for impeachment (if that's where we are headed), there are four grounds for impeachment: mental incapacity, physical incapacity, gross misconduct, or acting against the Constitution.
The incapacity ones obviously don't apply. As for acting against the Constitution, there are some legal caveats in my view. The 17th Amendment validated the 1999 coup, so that's off the cards. As for the PCO of 2007, the Supreme Court (rightly or wrongly) validated those measures, so using the 2007 PCO as grounds might actually invoke contempt of court against the current Supreme Court's decision, so this is very complex.
Gross misconduct might be a way if you drag in the Lal Masjid issue, but that's still not clear cut.
This may just be a big smokescreen to shy away from the ever worsening economic and security crises. Let's hope for the best, what more can we do as mere on lookers.