Barack Obama.
Assuming he's got other plans...
In terms of Labour MPs, that's the problem, there's a real shortage of anyone who looks like a credible replacement for Labour leader/PM.
I think
Alan Johnson would be a good choice: able to tick most of the boxes, and with a fairly broad appeal. But whoever replaces Brown, they'll have a very very hard job convincing the country to vote Labour yet again in the next general election. The thirst for change is too strong, and a change of face is almost certainly not going to be enough. The country has steadily become more conservative and reactionary over the last few years, particularly when it comes to issues like immigration and minorities. The Tories (led by
David Cameron - or "camera-on" as he will thus be known
) would have to mess up real bad to lose the next general election.
Most people seem to expect
David Miliband to be the next Labour leader - he's often touted as the natural heir to Blair, though I've never quite figured out why. He might be relatively youthful, but he completely lacks the Blair charisma - in fact he's the epitome of the manufactured career politician.
So I think Alan Johnson is who I'd like to see leader. Be interested to hear the views of other Brits on this.