Valve has decided to step-up development of DotA 2 and go against its original plans for a beta. The result? It's going to release a lot earlier than expected.
The creator of the original version, IceFrog, has said in the Dota 2 blog that one of the main pieces of feedback was that "people just want to play it."
He later went on to say that the team's new plan is to release the International version as fast as they can, through invites only for a short amount of time, then work on the game bit by bit and constantly release updates, similar to how Mojang is treating Minecraft.
If you want to get your name on the list for getting an invite, you will be needing to create a steam account and log in through here.
Source: DotA 2 Blog