will.I.am played keyboards on Magnificent. His contribution didn't result in Bono thrusting around moaning about his lumps.
If U2 goes for a bouncy, catchy sound, I don't think that would be the worst thing in the world. Look at the opening trio from Pop. Wonderfully catchy stuff with some meaty subject matter to all three. So long as U2 remained meaningful, also being catchy at the same time would just be icing.