The listed polygon pushing power has always been a bit of a BS statistic. The rule used to be to say how many triangles the GPU could toss out per second. But games run at mostly at 30 FPS or even 60 FPS . And on top of that, the triangle number used is implying no textures , no filters, no shaders, nothing. Just flat, possibly single color polygons. Textures and lighting take a sizable dent out of those figures but I'm not tech savvy enough to know just HOW big a dent that is. Filtering those textures and adding shaders is a monumental hit as well although the shaders can hide the low poly models quite well if used correctly.
One thing I do know from running the command console in crysis- that game is pushing between 700,000-1.2 million triangles in any given frame. I don't know what 5870X2 means in terms of raw polygon pushing (the bullshit number) but I do know that performance peaks for me around 650,000 polys a frame, I still manage 40-60 fps. Every 25000 or so extra triangles beyond that start costing me frames and when it hits that high point of 1.2 million or so the frame rate drops to a stuttery 30 fps.
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Another poster speculated on max poly output for character models for game engines on the next set of consoles and honestly , I've long figured developer can go 2 ways with this. Since the VAST majority of the best selling content on 360/ps3 ran at 30fps while barely being 720p (quite a bit was just shy of that resolution) I think we'll see a ton of games using roughly the same engines as today but they'll run at 1080P and at 60FPS with vsync and higher end filtering as well as much better antialiasing. In those cases obviously the models will be identical to what they are now. That number seems to be a large range but I'd say 10-20,000 polys is what constitutes normal these days.
Likewise though, we will of course see plenty of developers pushing the hardware in new ways with direct X 11 features cranked to the nuts, aiming for 30 FPS , possibly knock down the resolution to 720p. Would not be unheard of to see character models in such a scenario be 50-100,000 a piece. Given the time needed to make that level of art though I suspect less polys + improved shaders will be closer to what we'll get. So think, better clothing textures, better hair and cloth physics , better lighting and dust effects, sub surface scattering on skin , etc etc . All that extra detail won't need more polys, I'd say the raw polys would be better used making larger environments and rendering more things on screen at once.