So while we're not technically getting a new class with the upcoming expansion, we're actually getting two. Before, Blizzard had to balance out the changes they made to either one of those classes, but now they're much freer to send either class one way or the other. A few people are worried (aren't they always?) that with all the work being done on hybrids, single role classes will be left out, but Nethaera assures us that smaller, 25-player instances will actually give more individuals a chance to shine in their own roles.
Which leaves one more question: Considering this class balancing act is getting harder and harder, will Blizzard ever come up with another class for us? Of course, it wouldn't be until the next expansion (which we already know is years from now), but Tigole has specifically told us it's still an option on the table. Are there any other roles that need to be filled, say, by a Necromancer or a Monk type class? Or, by differentiating the Shaman and Paladin class roles, has Blizzard filled in all the blanks?