
Mainframes Of The Future
Unisys as the "little guy" demonstrates how the future will look like: x86 Xeon Processors running Enterprise Workloads.
Eventually even IBM will be forced to use that strategy, as it simply will not be economically feasible to create a S/390 CPU which is competitive with x86.
IBM itself had experimental binary code translation systems running S/370/390 workloads on other instruction sets (I think it was a RISC CPU) in their labs. DEC, HP and others managed to do the same very successfully (in technical terms).