Earlier today at CES 2014, Sony announced Playstation Now- a videogame streaming service that will allow you to play some of the classic hits from the PS3's library on your PS4 and PS3, and soon to come to the Vita, and even most 2014 models of the BRAVIA TV and other internet-connected devices. Because PS Now games are hosted in the cloud, you'll be able to play on multiple devices- even your tablet and smartphone.
Judging by the blog post on the Playstation website, PS Now will be a rental service that lets you rent individual titles, as well as a subscription service. Playstation Now will start a Beta program at the end of January, and is expected to fully roll out in the US sometime this summer.