PlayStation 4’s cloud service through Gaikai will bring an entire catalog of PlayStation 3 games through streaming to the PlayStation 3 and PlayStation 4. The planned service is currently being worked on and should be available in 2014. PlayStation Vita will follow shortly after.
At the PlayStation 4 reveal earlier in February, Sony had mentioned plans to make PlayStation games dating back to the original PlayStation. This plan is believed to be Sony’s answer for backwards compatibility.