I don't see the delay being related to PS4.5. Sony has known about PS4.5 way longer than anybody,
so would have announced PS4.5-related delay long ago (without needing to say it was PS4.5-related) if that was the case.
Simply releasing the PS4.5 "port" is easy enough, only requirement is 1080p and equal/higher FPS.
Any further special FX could be released as post release patch whenever they're done, no biggee.
Nobody would be surprised if the game was delayed even if PS4.5 never happened, that's all that I'm seeing here.
(now maybe with PS4.5 optimization work, it will be delayed 6 months instead of 4, but they still miss the holiday target regardless)