Although we're still waiting to see what the PS4 is going to look like, we definitely have a handle on the guts and how the next gen system will work. And that includes downloading PS4 games digitally. According to Sony exec Shuhei Yoshida, every single PS4 game will be available to download online.
In an interview with The Guardian Yoshida said:
We're shifting our platform more and more to the digital side -- PS4 will be similar to PS Vita in that every game will be available as a digital download, and some will also be available as a disc.
That would be nice for gamers who just like to click and buy (and not worry about the used game market, etc), but what might be even more interesting is a possible subscription model for video games. Yoshida described the possibility, saying:
As more and more services and contents become available digitally, we'll have more of an option to create attractive packages. So hypothetically we can look at different models -- like a cable TV company. We could have gold, silver or platinum levels of membership, something like that. We can do subscription services when we have more content -- especially now that we have the Gaikai technology available. With one subscription you have access to thousands of games -- that's our dream.