I own OD&D, Moldvay/Cook Classic, Mentzer Classic, Holmes Basic, 1E, 2E, 3.0E and 3.5E. So I would be breaking precedent if I didn't, and would no longer own every edition of D&D.
That said... it depends. If they 4E is more like 1E than 3E, I'll buy it. If it continues to morph into some other game, I probably won't. Already, I don't really consider 3E to be "D&D". If 4E is really just "generic fantasy game with unified core mechanic", well, I don't need it.