If I get a Dota 2 beta key, will I get to keep the game after it's released?

Solution 1:

Gabe Newell, Valve co-founder, announced in an interview published on 20 April 2012, that Dota 2 will be free to play.

"It's going to be free-to-play -- it'll have some twists, but that's the easiest way for people to think about it," Newell said.

Source

since there will be a ingameshop:

it is pretty safe to say it will be free2play. enter image description here

enter image description here

there are only cosmetic items to buy right now:

http://www.cyborgmatt.com/2012/03/dota-2-item-schema-update/#couriers

furthermore there will be trial and premium accounts. you will automatically be premium if you bought anything in the store:

http://www.cyborgmatt.com/2012/03/dota-2-item-schema-update/#trial-upgrade

Credits to Cyborgmatt.