They are most likely already working on the PC version and the ps4/xbone are closer in line to developing from PC>consoles then the ps3 was with it's system.
From a business standpoint it would just baffle me if they decided to not bring the game to next/gen pc, as they stand to only gain money from it, espeically from gamers that are moving to next gen and already bought GTA V who will double dip down the road as well as those who are holding out on it.
No, the PC version is already done (it is after all what they used to make all the trailers) and they're in no rush for a nextgen port. That's just how R* rolls. I would be VERY surprised if they announced it for PS4 and XBONE because those consoles were announced after the core development on the game was already done..