Everyone was expecting it, but hearing confirmation was good nonetheless: the PS4 will be able to play older PlayStation games via Gaikai streaming technology.
Though President of Sony's Worldwide Studios Shuhei Yoshida recently reiterated a point that was made some time ago, and which many seemed to have forgotten: Gaikai will work on a variety of machines, not just their upcoming console.
"… We would like to deliver PlayStation games to all devices. So we’re considering various things like PC, TVs, Blu-ray players, smartphones and tablets. We hope to continue to expand not only to Sony devices, but even to devices other than Sony’s. This is still being studied.
We previously spoke about PlayStation going from hardware to something closer to a service, regardless of the device — Of course PlayStation will still be the center, but I think we would like to expand to different things."
It all certainly makes sense, given how Netflix has already been mentioned as a streaming service that they're looking to somewhat emulate. And especially given how that service's popularity is largely due to it being platform agnostic.
Another thing to consider how much it will cost Sony to operate such a service; the company has plenty of resource, but still. And, even if the PS4 is a home run hit, there will only be so many consoles in use for the first few years. More devices that can support Gaikai means more revenue for the company.