I doubt that we'll see GTA 5 as a next-gen release. They didn't do the same for San Andreas when the 360 and PS3 were launched. And even now we can only play ported versions from the old consoles. So should we see GTA 5 on PS4 or 720, all these so-called benefits would not exist. Instead we'd be hundreds out of pocket and still playing a 360/PS3 game, oh but with a shiny new pad.
Is every decent game that comes out over the next 6 months going to be released again on the next Gen of consoles? My guess is the first few months of games will be gimicky tat like table tennis and dance/movement games that show off the technology more that the technical capabilities. The annual franchises will be first to release anything decent, FIFA and PES, any EA sports game really.
Rockstar have used 3 'GTA universes' so far that only last as long as that generation of consoles and never intersect in timeline or story. The 2D universe we saw on PS1, then the first 3D one which ran from GTA 3 to San Andreas (PS2 and XBox). And now we have the 3rd universe which encompasses Liberty City and the up-coming Los Santos (360 & PS3).
When GTA does come out on PS4 and 720, surely it will be in an all new 'GTA universe' completely separate from Nico, Johnny, etc. My bet is we see Saints Row 5 on next-gen before we see a next-gen GTA.