At the 2014 International Consumers Electronic Show, Sony announced the PS Now, a streaming service that will enable Playstation games to be played on the PS4, PS3 and the PS Vita.
PS Now will be available this Summer first for the PS4 and PS3, eventually the PS Vita and other Sony devices including TVs.
Details from the Sony blog include:
Leveraging Gaikai’s advanced cloud-based technology, PlayStation Now will allow you to:
Play video games instantly across multiple devices, similar to the way you might stream TV, movies, and music.
Stream full games to all of your compatible PlayStation devices including PS4, PS3, and PlayStation Vita as well as non-PlayStation devices, beginning with 2014 BRAVIA TV models and expanding to numerous other Internet-connected devices.
Always play the most updated version of your game. With games hosted in the cloud, you can take your game with you – just log in with your Sony Entertainment Network account on a compatible device and your games and saved progress will be easily available.
It's said a rental service will be available as will a subscription service.
Also be on the lookout as Beta testing begins at the end of January.