wfz on 09 July 2013
Keys are being phased out because the game is being officially released sometime before The International 3 (which starts on August 7).
At the very least, the game is supposed to enter an open beta.
Then again.. it's Valve. Who knows when the game will be released.
http://www.joindota.com/en/news/9971-dota-2-release-possibly-before-ti3
