I'm going to bash out a little thought experiment on one potential future scenario. Here it goes.
It's 2015. Both the long-lived Boeing C-17 and extremely long-lived Lockheed Martin C-130 production lines either have just shut down or are finally about to close.
Neither Boeing's engineers in Long Beach nor Lockheed's engineers in Marrietta have anything new in the pipeline. Sure, there's some paper drawings of stealthy tactical airlifters getting some buzz, but nothing within at least five to 10 years of coming to flying fruition.
So, both manufacturers decide to do what all US defense companies do in this situation: they go foreign!
Lockheed locks arms with the company they spurned more than 15 years before on a potential joint tanker bid. So the Lockheed/Airbus axis offers the USAF the in-production A400M, which of course will be assembled in Mobile or Marrietta (or both) and fitted with a new 10,000shp-class General Electric turboprop or the Pratt & Whitney Canada PWC800, which was actually the orignal A400M engine before "the Chirac affair".
Boeing, which will never partner with the likes of Airbus, has to be more clever. They decide to link up with the manufacturer they briefly considered for a Joint Cargo Aircraft bid: Ukraine's Antonov! The AN-70 is a rugged beast of an airframe, and Boeing's engineers believe they can smooth out its aerodynamic and mechanical quirks. Boeing parks the new AN-70 assembly line somewhere in the US southeast, with Charleston (South Carolina), Jacksonville or San Antonio on the shortlist.
Okay, that's my crazy theory for the day. Please tell me what you think. Poke as many holes as you like.