Red Porsche said a few posts above that this is where the Gaikai purchase Sony made might come in. They could stream PS3 games over the net.
That's a very expensive and complicated venture just to allow people to play old games that they are not making money off of, instead of buying new PS4 games.
If that happens, it's certainly not going to be free, and how are you going to be able to verify that you own the game for it to then allow you to stream it?
It doesn't make any kind of business sense to do this, unless as I said, they charge you a fair amount of money for it. But then, who is going to pay to play games they already own?