Theres nothing Intel can gain from buying nvidia. Therefore this will not happen.
That's not true in the slightest. There's ALOT that Intel could gain from acquiring nV, at the very least nV has a ton of patents (just like ATi or VIA) that Intel would love to have, Intel also has no foothold in add-in graphics either gaming or workstation, Intel's phone presence is next to nil outside PDA-phones, to name a few things Intel could use. The big issues are regulatory and price.
The Ultimate aim is to create an on die gpu which will replace gfx cards.
No it's not to replace gfx cards, it's to make it easier for system integrators to get a single chip solution, in the way that Intel can sell you the CPU, MoBo and VPU onboard, both Intel and now AMD want to simplify things and sell low end systems with their Mobo and multi-function CPU/VPU combo chip thus making it cheap and easy for barebone Dells, and other integrated devices (especially for business) as well as locking integrators into a single solution.
This may take 4-5 years, but this is the future.
The future for low, end, but not for enthusiast gamers, at least not until general computing returns as the method, perhaps as we approach more powerful chips then raytracing and other ideal methods may make arrays of CELL-like chips a more plausible solution, only at that time would a combo chip be wise for the high end, until then a top of the line CPU and separate top of the line VPU will be the solution of choice because of the focus benefit of each.
Fortunately for Intel, they already have the tech and resources to do it, so they don't need to buy nvidia.
Has little to do with it, there are other things that would be attractive to them, but for your example, Intel was already there, as was nV and ATi in the phone segment, and VIA in the ultra-efficient segment, only AMD was out in the cold on it's own for that, but there's also more reasons that that deal was good for AMD, and there's many reasons why Intel+nV would be good, despite it almost being impossible at this point in time.