I think WotC will be in trouble if this is challenged in court. Too much of DnD is too generic, too based on older concepts of fantasy, too based on other modern gaming implementations or too simply common sense games mechanisms. For example, look at armor class - they used to have armor class being low as good (remember THAC0?) but changed it to be like all the other implementations. Or look at DnD elves and tell me they are not heavily based on Tolkien. The rolling of dice to decide outcomes is far too generic to claim for themselves, even if they have more sides. Wizards, thieves, knights and bards are too ingrained in European culture to be claimed. How many of the ideas in DnD are so strongly DnD that they can't be used elsewhere.
I suspect we will just see lots of "new" roleplaying implementations that are far enough away from DnD terminology to avoid copyright, but not really any different in practice.
