It depends entirely on what the new date is. If it's Feb/Mar then obviously that is not enough time to add anything else, if it's another year and November then it seems more probable there is scope for additions/big changes.Well i must be the only one ho think that the delay is just to finish the game and achieve the solid minimum 60 Fps needed for the PSVR.
I don't think there will be any "extra" content.
The delay didn't even surprised me..but it's beginning to become a real shame.. Cause the first competence of the GT series (forza) got already 4 really good games on the "new generation consoles".
Hopefully PD makes the best GT ever to demonstrate that the await was worth! (personally and after GT5 & 6 really doubt it)