To participate in the chat, all you need do is visit the official page on Best Buy's forums when the chat itself goes live. If your question wasn't addressed in the Reddit AMA, or if you simply missed the opportunity to ask, this is an excellent chance to get all your questions answered. It's nice to see the developer community so active, particularly on the eve of a new expansion's launch. Be sure to hit up Best Buy Unboxed on September 18 whether you've got a question to ask, or you just want to watch the show.
It's open warfare between Alliance and Horde in Mists of Pandaria, World of Warcraft's next expansion. Jump into five new levels with new talents and class mechanics, try the new monk class, and create a pandaren character to ally with either Horde or Alliance. Look for expansion basics in our Mists FAQ, or dig into our spring press event coverage for more details!