You have a few good points, I exclusively use MSFS now and really do miss my PMDG hanger and am really looking forward to having them back in MSFS, one thing to note is you said PMDG are still holding back, as of RR last post he said "it's beginning to accelerate nicely" with MSFS development, and with this they showed a preview of the DC-6 in MSFS (on a different thread)
Since MSFS released I have been an advocate of use any sims you want, I don't get people who are MSFS vs P3D vs X-Plane, and neither of the latter 2 are obsolete as they both are miles ahead of MSFS in terms of 3rd Party Aircraft as you say, (I also don't get the people who thought that MSFS would have a full suite of PMDG, FSLabs, QW, Aerosoft, *IniBuild's* etc on or just after release)
Orbx like every other flight simulator company have decided what the future for them is and in most cases it's MSFS, still like Mawson said P3D and X-Plane are not obsolete yet, but I'm interested to know what we will be saying in 5 years time