2 very important things that seem to be overlooked here:
1) nVidia bought an architecture license. Thats (very) different from a core license. Forget Cortex A9 and A15, those are cores designed by ARM specifically targeting handheld devices, pretty good for what they were meant to do, but no more than that.
With an architecture license, you can build a custom core thats targeting any market, a laptop, PC, server, console, supercomputer; just a core that is compatible to ARMs ISA. You dont judge x86 performance potential by looking at Atom while ignoring Beckton. Likewise, dont judge ARM performance potential by looking at Cortex, nVidia could well try and build a Beckton competitor.
2) Seems like everyone forgot nVidia is the only big player to have purchased such license recently. A few months ago, Microsoft bought an ARM architecture license as well, which can only mean they are working on a custom ARM chip as well, and not only on an ARM windows OS. That might be only for xbox, but Id wager a guess they have every intention of doing like Apple, and becoming a vertically integrated company.