M.L. Martin
Hero
I'm not sure there are three categories though, but rather two: Advanced and Basic. 4E is the newest Basic, having evolved from 3E rules but shedding the Advanced's RFE appendages and returning to the gamist simplicity and "adventuring focus" of Basic.
I don't know; there's a sense of openness and encouragement to tinker with and customize the system in Basic that was both encouraged and discouraged in 1E (the latter on paper and in the side of gaming culture that focused on 'official', at least), encouraged more in 2E, both encouraged and discouraged in 3E again, and that I'm not seeing in 4E, at least at a remove. (Own the core books and AV, but have no play experience yet.)
Moreover I believe that the evolution of D&D has now come to a near standstill thanks to the GSL, and that while this will allow Wizards to capture more of the benefits created by the OGL Explosion, it will mean that much future progress will simply not happen. Many beautiful species will simply never be born.
Another way of looking at things that I've considered is that 4E is one of several evolutions from 3E; while the GSL means it will have no direct descendants of its own, it's possible that some other species may evolve in 3E with greater or lesser parallels to 4E.