Here's more news about what you can guess the system specs for Cataclysm will be. It's noteworthy to see that certain features on Macs will require a higher OS yet older OS's will still be able to function, while old processors will not.
Quote from: S4d1k (Source)
A little forewarning to those of you that play World of Warcraft on these systems;
Shortly before the release of Cataclysm, a patch will be released in which PowerPC processor based Macs will no longer be supported.
This update indicates the removal of PowerPC support from World of Warcraft.
Attempting to run the game after the update will bring up a message stating the hardware is no longer supported, and the game will not run.
Quote from: S4d1k (Source)
No problem. We are still supporting 10.4.11 and 10.5.8 until further notice. Some graphic features like the new water will require 10.6.4+.
Quote from: S4d1k (Source)
Even if you have PPC, you're still welcome to Blizzcon. I'll be happy to see you :) We only decided to drop PPC very recently so that's why we couldn't confirm anything before.
If you're on a Mac and you're not sure what processor you have here's a helpful guide from Apple (Click Here)







