Nobody is even close to touching intel in its niche of high single chip preformance at reasonable power usage. PPC was way way behind when it got replaced.
This despite the A10 running on FAR less power.
Apple's definitely within shouting distance and is a serious threat to just replace Intel entirely, at least for its own needs.
Apple has to surpass the Core i series to make any sense to switch.
And then there's the whole clusterfuck that would be porting all the x86 software to ARM. When Apple switched to Intel emulation of Power PC was usable via Rosetta but AFAIK emulation of x86 with ARM is extremely slow.
...Though at that point I suppose they'd basically be building an x86 co-processor into it. No idea if that would actually help performance or not.
http://www.macrumors.com/2016/09/15/iphone-7-faster-than-mac...