What about ARM and POWER? Google is deploying Power in its data center and I thin Nvidia is working on POWER CPUs for datacenters/supercomputers (they are both members of the recently formed "OpenPOWER Alliance").
As for ARM, I know there's a big reluctance to use ARM for the big names, because "meh, x86 is almost as good and we already have all the tools for it". But I think ARM is going to grow in a grassroots kind of way, from the very low-end (Raspberry Pi) and up. It will happen slowly, but a decade from now I think ARM will have a decent market share in the server market. x86 didn't kill the previous architecture in the enterprise overnight either - it took 2-3 decades to displace most of them.