The switching cost is too high to be competitive
the current PC era inertia is because we reached a performance level
that is comfortable for most use-cases for all commodity hardware,
so to justify switching an average consumer need something orders of magnitude better:
a x100 faster machine at same cost. a x10 faster machine might make sense with lower cost,
and x5 will not be even considered to migrate architectures(Apple can afford that though)
More important is the idea the x100 faster has to be visually/intuitively seen by consumers
to create mass market appeal: a niche use that accelerates specific class of software won't cut it,
so specialized hardware will not be adopted (that why specialized cards cost much $$$).
A new arch has to be.
1.competitive on generic(scalar) and bulk(vector/gpu) computation.
2.simpler than x86 but extensible
3.providing functions not in x86, accelerating common algorithms or software better.
4.more power efficient than x86, its a niche that battery-operated devices, datacenters and embedded require, but it also extends to desktop where heat increases failure rates.