Well, 65% of all statistics are made up...
So, my made-up statistic: Our group (5 people) will certainly switch. That means 100 % of the guys I play with will play 4E.
That said, there are 2 persons I know that were part of the gaming part but can no longer game regularly. One of them was skeptic, but on a very general base ("It will be all the same as 3E - a new 3.5.") since at that time, nobody knew any details. The other has already said he wants to buy the new core book (or at least the PHB) if it comes up...
But I am certain that there are groups out there where this is reserved. Because people in most groups have similar likes and dis-likes, and when one of them dislike a game, most of them will...