Hmm, I guess I was wrong on the clocks for Larabee...
About that 15-years from now scenario, I don't think any of us has any idea what it will be like. One thing is probably for sure though, one of us is wrong and I hope it's not me just because that would hamper upgrading as we know it now. Now you can buy a decent system, then when a better video card is released you buy that to replace your current and this way you can keep upgrading your system piece for piece. That will be a lot tougher when having the GPU integrated on the CPU.
The first fusion processors will be here at the end of 2009 and they will be aimed at laptops. It will probably take another 5 years before every PC and laptop has a GPU integrated along with their CPU and then we will see games that use those cores for physics and AI. What happens afterwards is hard do predict though, but discrete graphics cards won't be gone for at least 8 years from now and trying to look further than that only thickens the 'fog'.