PMDG, a developer who stays behind many Boeing aircraft to Prepar3D, like their famous 737, 747 or 777. Today, there is one update regarding the future development of these aeroplanes.
Robert Randazzo, a CEO of PMDG, has shared on PMDG forums some information regarding every their Boeing aircraft.
737NGXu
Randazzo announced, that they will work on the BBJ expansion soon, and the previews should come very soon. This expansion will contain the BBJ/BBJ2 and will include use of all auxiliary fuel tanks, support fully customizable interior and more. Also, they will improve more of their recently released NGXu base.
747 QOTSII
In the 747 section of the update, the developer stated that they are mainly focusing on improving the aircraft, they want to delete all the bugs, there are also going to be some code tweaks. Also, the developers want to improve the physics of this aircraft so it will be comparable to the 737NGXu physics (of course, edited to match the 747).
PMDG 777
The developers announced that they will work on PBR update for the 777 right after the update for 747 will roll out. Also, the developers want to add an extra level of visuals of this aircraft. This update should be the first after 20 months and will bring so many features and updates. Also, here, like on 747, there are going to be improved physics.
You can see more on the PMDG forums post here.