Playstation 3 Development Underway
At least in the United Kingdom, developers are already being handed development hardware for Sony's next-gen platform in anticipation of its debut at E3. From the article: "Sony plans to show the next-generation PlayStation off in public for the first time at its pre-E3 conference in Los Angeles in May, where it will almost certainly debut within a few hours of the public unveilings of Nintendo's Revolution and Microsoft's next-gen Xbox."
The 5-6 year lifespan on consoles is fairly typical, too. A brief timeline of consoles shows you have the NES at 6, SNES at 5, PS1 at 5. The trend continues, as you have noted, with the Cube and the PS2.
Of course, if you look at some of the other, "runner-up" consoles... say, Sega's... you'll find them often being released in 3-4 year increments.
Don't think of it as a flame---it's more like an argument that does 3d6 fire damage