Impressed by the trailer but I am treating this with heavy skepticism. Knowing what I know about flight sims (proper flight sims) I truly doubt you would get visual fidelity like that running on 4K with smooth frames. Even if MS re-coded flight sim from the ground up using 64 bit & win10, there simply isn't a single PC that could handle everything (aerodynamics, flight physics, AI traffic ground & air, 3d ground building/trees/structures etc, atc, high rest textures, complex flight dynamics & instrumentation, etc etc) as shown in that video. I want to believe it but as I said, I know about flight sims and I also know about how you can cleverly edit video footage and even take smooth 60fps recording from FSX by rendering a previously made flight path and creating it frame by frame, I just can't believe a proper flight sim can run 4k smoothly especially not on an Xbox. Unless it is not a proper flight sim but more a nice looking arcade flight sim game. Also not to mention that the highly detailed ground textures take up a HUGE amount of HD space, my FSX took over 1.2TB with just 30cm High Res ground textures (excluding accurate 3d models) and that was only UK/Netherlands/Germany/Switzerland/Austria/Australia & parts of the US. What you are seeing in that video is far better then 30cm and unless it only covers small areas of the globe, you simple wouldn't have the HD space esp on Xbox.
The only way it might run well on Xbox/PC and handle the huge amount of satellite data if the game is mostly streamed online, it would be possible then I think, then you will need some serious bandwidth. I seriously hope it runs as well as it does in that demo, but I ain't getting my hopes up. Time will tell.
PS Lets not forget the last time when MS & Dovetail released Flight Sim World, only to be cancelled & forgotten just over a year after its release!
PPS Plus how will this product get released, fully functional (like FSX) or chopped up, tons of paid DLC, will it allow mods/3rd party addons? I have not a doubt in my mind that MS will try to monetize it to hell and back.