Arm, MIPS, Risc, Risc-V chips would all be interesting.
Obviously there are super computers that use Arm CPU's. But from memory the fastest of non x86 chips is 2 to 3 ghz?. Would a cluster of smaller Arm chips work? or would this present problems like Saturn and Cell?
Arm seems logical, just from the sheer size of mobile industry.
Would be interesting to see Sony or Microsoft to get involved and see what that could custimize on something other than x86.