I don't think they will be -- the 767 line is pretty much dead, and the 7E7 line is still at least a year away.

IMHO Boeing will sell the E7 as a NG replacement for both the 757 and 767. It will fill the product gap between the newest stretch 737NGs, which can handle 180+ pax but don't generally op overwater (Aloha being an exception), and the 777.

Boeing seems to have ceded the bottom of the market to Embraer and the A318 and the top to the A380.

I can't imagine UA wants to complexify its fleet any further with more Airbus variants (A330/380). But I don't know what they will do about replacing the aging 757/767s for trunkline domestic service -- unless they push the 737 to its limits, as CO does, or accept the GE or RR engines that come with the 7E7.

I don't believe UA is an A380 customer. Too narrow a mission on UA's map to justify a whole new a/c. I think they'll run the 744s into the ground on Asia/Pac, the way NW is still flogging its poor 742s.