Intel's announced pricing for dual-socket 8-core SandyBridge-EP ranges from $1106 (1.8 GHz) to $2057 (2.9 GHz) per chip! There is little benefit of x86 compatibility in servers so this market seems ripe for a transition. Nvidia is working on Project Denver, which is an ARM chip for servers. I think other companies will make similar chips (perhaps even AMD). As the economic benefit of Moore's Law slows down, companies will have no choice but to use more efficient chips to provide continued price/performance improvements. It wouldn't surprise me if the majority of annual server shipments use ARM processors within 5 years.

AMD has intellectual property and expertise for cache-coherent HyperTransport, PCI Express, caches and high-speed DRAM interfaces. All of these could be applied to an ARM server chip. In an ideal world, AMD and Nvidia would work together on such a chip and would be second sources for each other on the finished product. Perhaps they could get some funding from Google and/or Facebook for developing this chip.