No single game has ever determined a console's future. Not even droves of good games have significant impact. In fact, due to the ultimate enemy of video gaming at large (disinterest/gamer drift), the best any given game can do is briefly boost attention towards a system. How long that boost lasts depends on a great deal of factors (particularly if it's a pack-in which showcases a system's capabilities; those tend to act as small-but-significant attention holders for the entirety of the console's lifespan).
GTA4 is a hyped game, make no mistake. It is a system seller of a sort. But it is hyped towards the existing core gaming demographic; to the mainstream, it's the embodiment of everything that's wrong with video games. Meaning its lasting impact is severely limited, given that the mainstream makes up the majority of system owners. On top of it not being a system feature showcasing game or a pack-in, all it has pushing its sales and the sales of systems is that aforementioned hype. And as Halo 3 demonstrated only half a year ago, hype alone isn't enough to allow a game to give a system a permanent edge against disinterest and gamer drift.
Sky Render - Sanity is for the weak.
