I am not an expert, but as end user I know that Intel is very fast, AMD is fast, my ARM tablets/phones are slow.
To race the Indy 500 I need a 12 cylinders engine and a lot of fuel, to commute to/from work the old 4 cylinders does the job using 1 Gal for 25 miles.
What about a new architecture? Also the Arm concept is old! Can it be enhanced to a high performance device and how many programs the will be available for it? is this a PowerPC repeat? is there a unified design standard? and so on.
I believe that he chip technology is the paramount factor in power reduction.
I think AMD, that is geared to offer high performance devices, will not be profitable making he ARM unless they capture a vary good chunk of the market.
Smart move by ARM: trying to put a foot into high end computing through a proxy :-) As for AMD, it does not make sense for them to drop x86, at least not for now - why should they?
By the way, I do not buy into the immortality of x86. I could well see a world without it, and during my life time. Efficient compilers, emulators and thin-client computing could smooth the transition.
ChromeOS might be viable as on a Net machine where one does all of the normal financial transactions and is fairly virus-proof. Beyond that, it's got to be the next version of Android. I mean, how much would it take to make Android a general desktop OS as slick as Win7 or OSX?