Taken from 1up.com for those that are still interested.
" There will only be a limited number of tickets available -- the initial announcement said more than 6,000 people would be attending. Considering a larger event like BlizzCon sees its tickets sold out in a matter of minutes, XP tickets are sure to be gone in the blink of an eye. Keep your eye on the XP website for directions on how to buy tickets next Tuesday. More details on the event, including location and travel packages, will also be provided then."