When they weren't happy with Bomb version 1.0 in 2003, they opted for the "revolving door" approach of multiple producers. And regardless of my personal feelings about Bomb v2.0, it definitely worked out for them. 9m in sales and close to a dozen Grammy wins? They'd take the same now in a heartbeat and sign-off. In short - I think Epworth/Tedder could be just the first two of a "brain trust" of producers they'll bring aboard.
And in the end, Bomb is widely considered to be one of their weakest albums. The sales figures can be attributed to a strong lead single and an influential marketing gimmick.
The revolving door approach worked for the modern, commercialized version of U2. It didn't work for the music.