Unfortunately, it isn't good news as Playstation Europe boss Jim Ryan has confirmed to MCV that Sony won't be building similar functionality to make the PS4 play PS3 games, saying that:
We are just taking a different path. To the extent that you are investing in software technology - which is what this is, it’s delivered through software not through hardware - we are trying to commit our resources and put our emphasis on delivering on the promises we made right at the start of this whole PS4 thing, to be the forward-looking, socially-connected console. We are placing our bets on things like SharePlay, on things like Play as you Download, and things like Suspend/Resume.