Their answers about the "biggest advancement" in Wrath are interesting though -- Brack says that he thinks the fact that they're introducing a new class to the game for the first time has been the biggest design challenge so far. Chilton is excited about the achievements (as am I) -- they should provide a lot of new ways for players to extend their gameplay and get rewarded for new accomplishments.
They also talk about a few things players don't usually associate with MMOs: social networks and consoles. Brack says that both are possibilities for Blizzard, though consoles wouldn't really work with World of Warcraft as we know it. Any MMO, they say, for consoles would have to be designed from the ground up to work with the hardware, and that's not something (including the next-gen MMO, we assume) that Blizzard is working on at the moment.