Realistically, we can't expect the same amount of content on PS4 like we have for PS3 now (though that was different 2 years back as well). Though DriveClub PS+ edition and Resogun are quite nice day-1 titles. I can see them giving away one new PSN title each month and maybe do more PS+ editions, that might "lure" people into buying DLC at least (e.g., KZ PS+ edition or MP only etc.).
I'm keeping my PS3 though. You have to remember that they will also have to appease PS3-only PS+ gamers, so there you will continue to see high amounts of content, maybe even more than now because they can just go all out.
Sure, that's old gen games, but still. Hopefully, later on we will be able to play all those collected PS+ PS3 games via Gaikai for free on PS4...
Also, I'm waiting for the exact services/features that are PS+ exclusive on PS4 and/or benefits for other subscriptions (e.g. Gaikai. Music Unlimited got also more interesting for me, now that you can stream it ingame).