I agree: Being able to run on ARM is important - be hardware agnostic if possible.
As a very satisfied owner of a Surface RT tablet, two quotes stood out for me from the article:
"As mentioned, previous ARM-powered Windows tablets failed partly due to poor marketing and customer communication. "
"Even if Intel chips serve Microsoft's needs for the present, continued ARM development is prudent over the long term." (which followed a discussion of how ARM chips are getting to be as powerful as desktop chips, at least in the Apple hardware.
Windows RT is an amazing OS, and the RT based Surface and Nokia tablets are really, really great pieces. Surface RT and WWinodws on ARM certainly did not fail due to any lack of technicalogical merit - they are first rate machines! Windows 8.1 RT is really the best of both worlds - tablet and PC. Having Office bundled makes it an incredible bargain. It runs great. It would be short sighted to abandon it, - instead, open it up to legacy Windows x86 code (if it is feasible) and continue to run with it. The customer can only win, though it may cost Microsoft in the short/medium run.