So the result was quite favorable for NV, but they wanted more aut of the deal? If I understand correctly, they got chipsets back, but chipsets won't help them any more. It's only a minor part now that CPUs got all the goodies. Eventually more and more peripherals will migrate from chipset to CPU and even NV must surely realize that.
But what on earth would make them go for x86? Sure, it's a huge market right now, but also a cutthroat one at that! AMD has been struggling for decades against the behemoth that is Intel with more or less success. In fact I only know of one instance that they had a short lead (the original Opteron / Athlon 64). VIA retired to a niche years ago when they found they had no chance competing against those two. Any other attempt (remember Transmeta?) went under as well.
Even getting x86 licenses would cost them billions in R&D to get somewhere around Intel's previous generation CPUs or even the generation before. So why even bother?
Instead I think NV should focus on ARM. They have been doing it and doing it relatively well. Sure, they have high power consumption, but that doesn't go for every market segment. Their Tegra 2 won't find a place in a smartphone, but beefed up it sure could find a place in netbooks and even PCs of tomorrow.
ARM AFAIK doesn't restrict core optimizations. Since NV knows a lot about caches and similar stuff thay could take what they already have and beef it up into a chip to behold! An ARM chip with a decent graphics core and performing better than, say, Zacate, would surely attract plenty of attention, especialy once Windows 8 comes out. If it consumed less than 4W, all the better.
So, NVidia: why even bother with something that may never be competitive? Instead use the knowledge you already have and differentiate yourselves!