The PS+ version is supposed to have every feature of the game, just with lesser tracks and cars. So, yes, if the social features are not ready the ps+ version cannot be launched. Bu if some of the cars and tracks were incomplete, then they could launch the psn version.
From the footages we have seen, i think the game just isn't poished enough yet. We haven't seen any mp footage at all either. So much for Cerny's time to triangle
I think the time to triangle is probably still correct, the social features are a different scale of programming. Needs a different kind of thinking to do.
If Sony are still working on the OS and there have been changes to the API and underlying libraries it might have a bigger knock on effect to a game like DC that is leveraging social features so much.