I'm sure AMD is already taking low power plus high performance chips very seriously, not only for mobile but everywhere. The recent news about widespread power outages in India just helps to drive home the point. Data centers suck huge amounts of power and generate lots of waste heat, so every element of those is getting intense scrutiny regarding power/performance metrics.
Bringing Mr. Keller back into the fold, AMD is sending a clear message that the top management is committed to the work. As for getting the work done, I'm sure there are many very talented AMD engineers already working on high performance plus low power processors. And AMD will attract some more now that Mr. Keller is on board.
Jim Keller is an industry veteran and has been around many succesful designs -Dec Alpha, SiByte, PA-Semi, Apple but he has not been the sole resonsible architect for any of these (except maybe PA-Semi). Crediting him with the low power CPUs and chips from apple is stretching it.
I don't see this making any difference to AMD's short or long term viability.
@goafrit, no dobut Chip design is not a one man game but its always good to have a leader who can choose the best team. I am sure AMD has enough talented resource pool which along with Keller will make good team.