I highly doubt it will last 10 years. The reason? Because PC games are going to have way better graphics than the PS3/360 in the years to come. When Sonic Adventure came out in 12/23/98 it blew away everything that was on the PC. The best looking PC game at the time was Half-life. There is no comparison between Half-life and Sonic Adventure. Gaming capable PCs were extremely expensive at that time. At the time I had a $2000 PC and I couldn't even run Half-life on max settings(I think that basically means max resolution). The Dreamcast was $200.
Doom 3 was released on 08/03/04. The Xbox was able to run it. Reviewers said it was pretty close to the PC version. Now, I'm not exactly sure how a standard definition TV compares to a monitor in terms of resolution, but apparently it's 480 scanlines. I'm guessing it requires the same amount of power to display a game on a standard definition TV as it does to display it on a monitor at 640x480 resolution. Doom 3 can be run on ridiculously slow PCs at that resolution, but it looks horribly pixelated. However, people said that Doom 3 looked almost as good as the PC version. Why? Because you don't see the pixels on an SDTV. The scanlines make it look like your running on a high resolution. If you play an SNES game on an emulator it will look horribly pixelated, but emulators have something called "TV mode," which changes the graphics to how they would look on an SDTV by blurring them and adding scanlines. When you do that they look the way you remember them. However, HDTVs do not have scanlines. You can't use scanlines to create the illusion that the game looks as good as the PC version despite running on a very low resolution. In other words, a game on the 360/PS3 needs to be running at the same settings as the PC version to look just as good. The Unreal 3 engine isn't supposed to have massive system requirements. It's much like the Doom 3 engine which looked way better than games with comparable graphics yet ran at way lower requirements. I'm sure that for less than the price of the PS3 you could get a processor/video card combination that would run it as well as it would run if it were released on the PS3. Unreal Tournament 3 is being released on the PS3 btw. In short, it would be cheaper to upgrade your PC to get good graphics than it would be to buy a PS3.
The Creators of Crysis, which is being released on the PC pretty soon, said the PS3 and 360 would be unable to handle it. Crysis pretty much puts Gears of War to shame. So basically the PC is capable of running graphics better than a $600 system almost immediately, which is completely different from last generation where a $200 system had better graphics than an extremely expensive PC. At the moment, it would cost more to upgrade your PC to Crysis level than buying a PS3 but that's going to change a year after Crysis is released. But 3 years from now? Come on, by then an upgrade to a PC that can run Crysis on max settings will be nothing and by then there will be PC games that blow away even Crysis. As for 10 years from now, it's unthinkable as to what a PC will be able to do. The majority of gamers are too clueless to know that they can open up their PC and put in a new video card, but they're still they're going to be looking at PC games and wondering why their system can't do that.
The graphics of the PS3/360 will improve a bit as the developers figure out the systems. Still, the PS2 released 2 of its best looking games, Metal Gear Solid 2 and Ico, early in it's life: http://ps2.ign.com/articles/606/606189p1.html and there's not even that huge of a difference between MGS2 and MGS3. PC games this generation will always be ahead of the consoles.
In short, I say 6-7 years before Sony releases the PS4.