Voting is a numbers game. Compared to what is needed to contest and win elections in Pakistan, he will never get those numbers from Dubai, UK, US and all over the overseas Pakistanis combined and if they all voted for him only, which is hardly the case by a long shot.
There is also a school of thought, that Musharraf is afraid to go back home - mostly its sensible since as webby mentioned it won't be simple and fair, but still his persona is that he faces challenges head on - so him staying out of Pakistan further worsens his case for re-election.
To regain his popularity he has to work in Pakistan. Nowhere else.
Pakistani electorate goes with the wind. This is the essence of our politics. I myself am not too sure whether Musharraf has a chance, but things can and do change in Pakistan very quickly.
The reason there is so much anti-Musharraf propaganda is because he himself needs to take on his detractors and put his side of the story out. Right now, its simply "Uss nay ghutnay take diya amreeka kay saamnay" and no response from the Musharraf camp.
I think one thing that was admirable about Musharraf, and also recognized by his opponents, was that he tended to accept responsibility for his errors, which is something that rarely ever happens in Pakistan. Up until 2007, he had solid Pakistani backing despite the fact that it had been 7 years since Pakistan had joined the GWOT. So the issue is one of getting press time, being in the headlines and negating the views being aired by his detractors.
Its doable, but entails a lot of risk and skill. I think he has both, however age and physical threat are a couple of roadblocks.
People are fully entitled to take their shoes with them and come back barefoot as these feelings do come up and do so for most politician in Pakistan (I am sure there are always people in the crowd who'd like nothing better than a well aimed "Bata boot" in the face of any of the other politicians either.