you realize this is all possible because rockstar has been working on the 360 and ps3 for the past 6 years right? rockstar has no experience developing for the xbox one and the ps4, sh*t would probably be even more fu*ked up than gta 4 was if it came out on a next gen system. it's better if they just developed the game for the 360 and ps3 because those are systems they already know very well. gta 4 couldn't do diving, car customization, and tattoos in gta 4 because that's pretty much the first game they ever made with that engine besides that table tennis game. now they made several other games with the same engine and they know the sh*t inside and out.
just because a new system is out doesn't mean every game has to come out on it now.