Probably not going to happen anytime soon.
World of Warcraft (WoW) from Blizzard is a new, very good and very modern MMORPG that is available for Mac from the get-go - and you can play with PC users as well. That's the place to be for Mac MMORPG players.
My only Mac is an iBook 900Mhz G3 (using it to post this), which isnt capable of playing WoW. Doing EQ2 on my PC for the moment.