I would guess that if they were projecting lots of growth in the line, they wouldn't have done a disruptive factory move.
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.
I wouldn't rely on the Watson connection to influence their chip division strategy.
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.
....which they moved to Guadalajara, Mexico. Given the money they put into Watson, I would expect they keep the POWER machines.