ARM is now the only CPU in the world that will have deep penetration in the mobile devices, the PC, servers and supercomputers.
Arguably, Intel already has that with Medfield + Clover Trail and IvyBridge variants.
nVidia only really wanted to make CPUs to pair with their Tesla GPUs for a specific market and uses... Since Denver will not match Intel's Haswell/Broadwell performance it kinda begs the question how it differs from x86 Denver.
aside from a different architecture they will always be playing second fiddle to Intel... And on the ARM side of things, there are more big players than on x86, albeit maybe not one has the advantages and monopoly of Intel on x86...
And lets not forget, Intel owns an ARM license and should they decide one day to reenter that market with their fab/process advantage they could easily decimate competition...
The power usage thing is a myth, Intel proved with Medfield and Clover trail x86 scales to sub 1W TDP while delivering A9/A15 rivaling performance - and that with an ancient in-order Atom core