Question then: if they do that, when could they release a new game? They tend to release a game a year, so there could very well be a next gen game from them next year...
I'm not expecting a new game from Rockstar in the first year of next-gen consoles. It was Rockstar presents Table Tennis for PS3/360, right? I don't imagine they'll release a Red Dead, Bully, Manhunt, Agent anytime soon. Midnight Club is probably the best bet.
It also seems that GTA V is going to be their last PS3/360 gen title. You'll probably see their first next-gen title in 2015.
I don't see why they'd sit on the next-gen versions for so long if the architectures are closer to PC this time around. ~6 months is enough time for people to get past the "Ugh, I should've never bought the last gen versions" reaction, but enough time to release with a GTA Online DLC pack or expansion. Unless they literally haven't even started them yet, which I highly doubt.
But sure, we could see the PC version sooner. That wouldn't surprise me either. Regarding that though, none of the other 3D GTA PC ports have come out within 2 months sooooooo, yeah. Time will tell.
I wouldn't put it past Rockstar to delay any next-gen version. 6 months seems too soon to tell people you want them to upgrade.
As for the PC version, I look at Max Payne 3 being on PC near day one. And Red Dead Redemption never coming to PC. I expect a PC release relatively soon, even if another Rockstar studio is working on it. It could be 6 months, like GTA IV, but that didn't seem as well planned as GTA V has been.