Well, I think after reading this article (see link below in ref section), the Great US Air Tanker saga is going to end up with a split buy between Boeing and Northrop Grumman.
Its (really) no longer about getting what the Air Force really needs. It's about politics and keep voters supplied with jobs in key states. That means both Boeing and Northrop Grumman will both win the KC-X tanker project.
The KC-135s are REALLY long in the tooth now and needs to be replaced quickly as possible. Neither company is in favor of the dual build contract. Boeing and Northrop Grumman want a winner take all approach. The USAF supply chain would prefer just a single type of aircraft to support for this mission instead of two.
By doing the split buy, the Air Force gets new tankers in the air quicker. Current projections mean that at least 15 new tankers can be built a year. It will take decades to replace ALL of the KC-135.
Image is of the Boeing offering based upon the Boeing 767 airframe.