Backwards compatibility has killed the PS4 dream for me. With Miles still in the tank on GTA5 and I'm yet to get GT6 I'll be playing the PS3 for a fair few months yet. If GT6 came out on the PS4 i'd have one now. GT6 is the hook for my but I never play two games at the same time, once ive done one I move onto the next and dont look back, I really want to get GT6 now but I still dont want to put GTA5 down.
Apparently Sony will be releasing a system like Onlive so you'll be able to play all the old games via that online but from experience thing from Sony can take a very long time.