Are there going to be generalists? Sure. Many of them, working in small- or single-person teams. And perhaps since they will likely do the bulk of UX work in their organizations, "user experience designer" is a fine title and role for them. But my hunch is that, like general practitioners in the medical field, what generalists in the UX field will work on will be constrained to a set of limited problems. For anything really complex, specialists will deal with it. I'm pretty sure this is the situation we're in right now, in fact.
I was reminded of this bit of wisdom from Dan Saffer while reading a recent over-hyped blog post.