Joystiq carried an article citing the researches of Jason Kraft and Chris Kwak. It analyses the worth of Grand Theft Auto and its future.

It says with a couple of next-gen GTA games that can be realistically expected to come up against the 3 current-gent titles, its maker Take-Two could develop unique PSP games between major next-gen console releases. It says;
Shorter development cycles on PSP enable Take-Two to release PSP titles more frequently. The regularity with which Take-Two releases GTA titles on PSP will be critical to the franchise's revenue growth in the next-gen cycle and underlies our revenue growth forecast.
Furthermore, they analyze the current worth of the GTA franchise is about a whopping 900 million dollars or somewhere between $10 - $13 per share. So GTA is worth 62 percent to 81 per cent of the company's total value.
Controversies aside, the fact is that GTA is rocking and not just alive and kicking. Besides, the future of GTA is perhaps brighter than most of the super-hit games that are already in the market or for that matter is being developed for the next-gen consoles.