It's best not to wait if you're going to get the game, as there has been no multi-console plans for The Last of Us at any point. Whether somewhere down the line PlayStation 3 games are ported to the PlayStation 4 digitally or by some other form of transference, that would be then. As of now however, The Last of Us is a PlayStation 3 exclusive.
Yeah, I held off on preordering until tonight (digital PSN version) because I was hoping for a surprise PS4 version announcement at E3. I decided to cut my loss and go ahead and get it. It will probably be the last game I buy for PS3 (yay large backlog of games I keep telling myself I'll play soon™).