Hopefully the beta is free to download, and we don't have to buy into it or anything. Knowing PD's history, I'd say it's very likely it'll be free, and that way we will all be able to see how good it is at that stage, how well it develops, and we'll be able to assess if it's worth buying the full game. I think that's the best bit out of the small amount of news we got about the game so far.
Until then, we really have no idea what the game is even going to be like. People are still speculating if it'll have in game currency and a progression like other GT games, or if it'll be more open and more motorsport oriented like Pcars. I have a feeling that PD will release precious little info on the game before the beta is out, so they can throw up a few surprises. When we've all got access to the beta though, this thread will really explode.