From what I understand its going to be free. The moderators at the official forum said that it is free. And plus, its not a mmo and its also on battlenet...
Don't know the release date though im sure they will say when it is once they tell about the other 3 characters, which should be sometime soon.
Blizzard's sticking with the usual quote, "It'll ship when it's done." Although this is somewhat of a nuisance, it makes sense. Blizzard are doing it the usual way, and all of their games turn out to be a big success. Why stop what's going good? I'm sure it'll be pushed back like their usual release dates in the past, when it's announced. As long as it's free to play, is as of now, I'm cool with it. Just don't mess it up, Big Blizz. EDIT: And I'm sure they'll announce more at Blizzcon in October, since Activision Blizzard isn't attending E3.