Developers started flocking to the App Store because they saw a great opportunity, a gold rush (fueled like never before by media).
If a consistent part of them would leave now (and I believe they won't), it would be even more appealing for other to join since there would be less competition.
I decided to keep my predictions out of the post, but in reality I agree it is unlikely that there will be a mass exodus of developers. I do, however, wish developers would concede that they're getting what they ask for if they end up on the wrong side of an App Store policy decision. And in my more optimistic moments I hope developers understand that we do have some power to get behind fairer policies.