Remember, if you're looking for a new simulator (totally new), you might check out Aerofly 2.
And note that they have recently released a new SDK that is building up. Its not 100% yet, but the exporters are there and a lot of information. I'm presently trying to get my plane in it. (Setting up landing gear is a challenge).
Perhaps DoveTail Games should hold on to their current investment done in their FlightSchool product.
They could decide to fully integrate FlightSchool into their future version of FSX:SE flightsimulator.