I disagree with this position unless I am misunderstanding that it is being taken within some limited context that I am missing.
x86 is the defacto standard because it was the affordable business/corporate computer for employees in the mid-80's.
From your accounting dept, payroll services, to manual prep and publication, to your marketing team, to your engineering dept...they could all be serviced by the IT dept with a common hardware platform.
Hardware servicing is identical regardless of whether it is powerPC, intel x86, ARM, SPARC, or what have you.
Software is where it is at. MS realized that, bill gates success was when he retained the rights to the OS rather then relinquishing them to IBM, and then porting the platform to x86.
x86 had success in the early 80s due to what you said. The only reason it remained in power into the 90s is because of windows. The only reason it remained in power through the 2000s was because of games. And even with the above games were a HUGE factor in pushing for faster and better hardware, my first games were all DOS games.
New faster hardware wasn't made for office and excel, it was made for demanding tasks. Enterprise stuff benefits from such extra power but it only needs to be relatively more powerful then current tech, and as such is not a big driver in of itself.
Gaming is what has pushed CPU and GPU and RAM to ever increasing heights and when they became mainstream office software expanded to make use of the new hardware. Yes office 2010 is far better than Einstein document editor for MSDOS (my first word-like program back in 1991) but nobody developed or bought faster hardware for those.
The whole "hardware is fast enough for mobile already" thing people are saying is merely the incorrect explanation given by analysts to the fact that people are not upgrading their laptops and cell phones for greater raw performance. Without even realizing that the REASON people are not upgrading is merely a symptom of people not wanting to game on such devices when they can use their big screen TV + console or a proper PC with a nice keyboard, mouse, and monitor.
I still service corporate computers running Win 3.11 on occasion.
A consortium of gaming companies (EA, BlizzardActivation, Ubisoft, etc) could topple intel and MS in under a year if they made their games for ARM & Linux or SPARC & Solaris or some other platform/OS combo.