What they are not good on is their drivers on Linux. So while GPUs on ARM will get better it will definitely be on closed hardware/OS.Yes they will - Nvidia doesn't do CPUs.
It would make good sense for Nvidia to combine ARM core with Nvidias GPU acceleration prowess (think supercomputers) - rival to AMD / ATI combo (APUs etc).
Also good play for machine learning and assisted driving tech - which Nvidia is big in