I have a wide probability distribution. There's a chance, of course, that my basic intuitions are wrong in such a way that it's actually impossible to emulate a human brain and have it preserve the "essential" stuff. Aside from that (which I give less than 5% credence), I'd be quite surprised if it took less than 5 years or more than 100 years of technological development, since we currently have a reasonable roadmap and since there are plenty of other technologies (like nanotech) that would enable massive shortcuts.

(If there were a nuclear war or an anti-scientific dystopia, of course, that would halt the timeline of progress. That's why I say years of technological development, not of clock time.)