Current Gen consoles... hmmm don't think so, seeing as Rockstar stated that they're "gonna reach a level of detail that the other GTAs only hinted at". So cramming gta4 on systems that could barely handle gtasa...
They 'd have to scale down textures, models, world detail and at that point it'll look nothing like its NEXTGEN counterparts.
I don't think so. At most, an eventual GTA San Andreas stories (maybe) for the PS2, after the PSP.