The real question is can Sony or Microsoft make another console with a competitive price look all that much better than the current gen. I don't think the answer will be yes for a long time. No ones' going to introduce a console at $600 ever again. KZ2 just showed that top notch animations/cutting edge effects/lighting can overshadow gains from standard graphical advancements like fill rate, texture size, ect. .
And remember pushing the capabilities further pushes the need to spend more making the game with finer details. 3rd parties will not 'hop on board', I don't think publishers want a next-gen to happen soon and its going to show: this gens going to last a lot longer, unless someone (ms/sony) try's to pull a 'wii' esqe new control scheme on things. Even with the wii it was hard for Nintendo to get meaningful third parties for awhile with a 'risky' console.
10 years sounds plausible at this stage of the game, what we have now is here to stay.
