I've posted previously about this, but the rumors aren't dying... obviously there could be something happening, but until it does it stays in rumor land for now.
NVIDIA don't have a CPU, they only have dedicated GPU's/Tegra range - this puts them between a rock and a very, very hard place come next year when AMD launches their Fusion APU range. With the integrated graphics exploding like there's no tomorrow, it is paving the way for a completely different market than we're used to.
Kitguru have a pretty big article on the rumor, I would suggest if you're a fan of GPU's or NVIDIA, to give it a good read.
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