Boeing has yet to announce a 757 replacement in 2016 as many has suggest will come. It remains a big question for which Boeing has indicated it has time to consider. Now it seems it will say something by years end. With that a meaning is derived from this hint. Boeing prefers to work out all details about a "Tweener" aircraft first rather than build it first and then modify it later. This becomes reading between Boeing's lines when it sounds plausible. In other words the Boeing corporation new attack formula on aviation's market is getting it right on paper first, and then acting second.
It has been over ten years since the original 757 ceased production and Boeing has had plenty of time and resource ciphering the proposal. The "things change" factor is the ghost which continues to chase new airplanes that is not unlike tagging a rainbow. The 787, A-321, and other types confuse the picture of what passengers and airlines want. Boeing could have built a Tweener five years ago but airplane wars was in the middle of a big battle with the 787 and A350. Then the 777X assault began having a topping of Max-bits to boot.
The 737-9 is an unmitigated market pause suggesting Boeing needs more than a A-321 rival, it needed fulfillment with a "game changing" expectation instead, as customers have begun to expect from Boeing everything Boeing is "Game Changing". Once again back to the 757 replacement.
Now comes a tid bit, at the end of 2016 when "Boeing will know what it will do with a new class of airplane". A "Make it" rather than "break it" mentality. It should announce something the competition can't do at this time or into the next ten years. Build something special and they will come. Boeing has the parts bin, technology and design mechanism to do this, but it doesn't have the capital or risk managed for such a venture. Data will address the winds of risk before it will proceed, since it has so much on the production and R&D table at this time. Boeing should provide an answer by stating a solution having a five year time line this December.