They'd probably want to do it as a new game, not a D&D setting, partly to be sure of doing it justice and partly for the reason John gave. But if they do that, they're competing with themselves over the, not very large by WotC standards, fantasy RPG pie; avoiding that kind of market fragmentation has been a cornerstone of their business strategy since they bought TSR and I see no reason they would change that now. So they only would be likely to do this if they thought they could bring in a significant number of people who aren't current or likely-future D&D players, and at the moment there is little reason for anything but pessimism on that point. So, while I personally would buy it in a second, I don't think it's going to happen.
