For me, immersion is most important.. I want to feel like I'm flying a plane. therefore,
1)will TrackIR be implemented (and VR, for when I find the cash to splurge!)
2) How will scenery be visualized? So far FTX Orbyx has hit the sweet spot on photo textures and hand placed landmarks, with suitable autogen to fill in the blanks. More abstract visuals are never as satisfying in the long term. What approach will the new sim take, and will it also concentrate on region-packs (or area unlocks, etc)
3) a living world. Car traffic, air traffic, boats, animated waves, windmills, flight crew, sea gulls etc add tremendously. Microsoft Flight was a step up on the world topology/cityscape but was utterly dead and frozen in place.
4) damage model + effects. i don't care too much about the politics of it, but half the entertainment value of combat sims is seeing your crumpled wreck when you mess up. I understand an airliner turning into a fireball is distasteful but having a plane freeze like a block when it hits the ground after a failure or error is not immersive and does not put give the event the gravitas it deserves.. can there be a middle ground, or a toggle?
5) can we have AI wingmates? I don't have the time to play online, but it would be great to have AI wingmen to lead maneouvres and give the player someone to formate to or who will follow.
I know this usually doesn't apply except for the military, but I can imagine a couple of friends who have cessnas or small planes might like to fly together to, no?
6) will you be modelling choppers?
7) will you be allowing for a variation of cloud looks/formations? I'm spoiled by REX and have trouble feeling immersed when the sky is littered with evenly spaced puff balls.