If you look at the development costs of a simulator like MSFS2020, you'd find that to make that business profitable MS will need a more or less constant inflow of cash. LM did very well, as far as I know, in charging approximately every two years another license fee after they release a new major P3D version. The same would apply to MS. If they (and they know how to do it) want to continue development for the new sim and recover all costs associated to the initial development, the bandwidth infrastructure and the associated annual expenses of the streaming, they should ask for something like a monthly subscription and an initial "access" payment (GamePass in the MS jargon?).
For sure, and they've already had the experience, they won't look for something similar to what happened with FSX, in those days when you purchased a set of disks and forget about future payments to them to keep the simulator alive and continuously progressing.