I'd wait a bit longer, if I were you. I've got a PS4 and bought it at launch. While I do like it, and while I think PS+ is a great value, I have exactly ONE retail game: Wolfenstein. I had Killzone, Assassin's Creed, Knack, and Tomb Raider, but once I finished them I had no incentive to hold on to them. And frankly, those games weren't that great to begin with.
There are some great indies and downloadables, and many of those are free with PS+. But honestly, I don't see a killer app yet. Destiny is coming, but that's multiplatform. I think Driveclub and Little Big Planet 3 are the only exclusives I'm interested in this fall...unless I'm forgetting something.
But it seems like everything is hitting in 2015, so I think you're probably good waiting until then.