The buzz around digital distribution of video seems to be that rentals stand on the horizon, and will likely appear on mainstream distribution centers in 2008. This is very exciting. I've also been thinking that such a model might be a good fit for gaming, depending on the execution.
Game rentals currently have some quirks. There are really three models of game rentals available for a consumer today. There is the Blockbuster model, with physical store locations for game rentals on a per-game basis with rental due dates; the GameFly model, which works very similarly to Netflix for games, with a monthly fee and physical distribution for unrestricted lengths of time via the postal service; and Gametap, which has a monthly fee for digital distribution, and an ad-supported option for free play of selected games.
Of these models, Gametap's comes closest to what I'd consider an ideal implementation, but its somewhat limited catalog of games and requirement of a PC (which at least for me is a far cry from able to support the same graphical load as the newest generation of consoles) stunt its potential. Gametape has done some great things, though. I've particularly been impressed by its revival of Sam and Max, and proving with said revival that episodic game development is a viable option.
However, this model of distribution is still far from widespread. While I don't think 2008 will be the year of the digital game rental, I think it's worth watching the success of online video rentals carefully. Should they do well, I don't doubt that some pioneering individual or institution might just figure out and implement a clever model for digital game rentals on a wide scale.