IBM was pretty close to cutting off most funding to future development, and they just closed the factory in Minnesota that made the servers. They are pretty much the last survivor of the Unix wars.
There are major customers using this stuff and scaling up, but the industry as a whole is shifting to scale out. There might be a good story here with POWER8, but can you trust that the platform will be around?
....which they moved to Guadalajara, Mexico. Given the money they put into Watson, I would expect they keep the POWER machines.
It's not something they spread around, but from what I recall from a Q+A with IBM engineers the Watson prototype was developed on AMD xSeries servers, and only moved to pSeries machines late in the development before the Jeopardy! matches.
The business growth for power was displacing PA-RISC, SPARC and Itanium... IBM is the last man standing, but are competing against whomever is supplying AMazon, etc for barebones x87. In the IBM line, it's jammed between commodity x86 and high margin zSeries.