System Requirements for Lich King?

It looks like World of Warcraft players are getting more of the same graphics and OS wise with the Wrath of the Lich King expansion. According to Blizzard poster Nethaera on the official WoW forums as a response to a question about the operating system and graphics requirements for Wrath of the Lich King:
The specifics for what will be required for running the expansion have yet to be worked out but it seems unlikely that we will be moving over to have everyone only able to play if they have Vista. We try to keep the game as accessible to as many people as possible and take that into account when developing our content.
Rob Pardo, Blizzard’s senior vice-president of game design, also recently quashed rumors about a graphics engine upgrade asserting there will be no system requirement change for Wrath of the Lich King.