Likely what's going on is that Sony is no longer going to support PS3 on PS+, so they're trying to think of a good way to compensate for that, and my guess is that they'll make all the PS3 games free on the PS store for PS+ users. And after that it's just going to be PS4 and Vita games, starting with Knack, Killzone, The Order and Driveclub.
That's my guess anyway. I could be wrong.
Yeah... "could"