According to several sources (example at the link below), FS 2020 will include a marketplace. There don’t seem to be hard details from Microsoft yet, at least that are public. Some theorize that it will include a mix of paid and free content. I also recall seeing this past week (but don’t recall where) that vendors set their own price (but I assume MS takes their cut, maybe similar to Steam). It’s also theorized that the official marketplace won’t be the sole source of add-on content; that users can procure from wherever and install into the appropriate folders, just like now.
Sorry I’m doing these out-of-order, but wanted to give some opinion about this: I’ve had X-Plane 11 for a few weeks (along with Prepar3d). I’ve played it a lot the past 5 days. In terms of accuracy of the flight model (for consumer-levels of accuracy), it feels the closest to me. Doing an approach in a C-172 feels just like my time doing just that IRL - complete with my over-control. It’s a bit “foggy” compared to others, but having flown mostly in FL, that’s pretty realistic.
But X-Plane doesn’t have the easy-to-use flight planner of others, and it’s in-flight map is really flight maps/sectionals - which is cool, but that’s the ONLY map - you can’t easily use it for sightseeing. I’ve also had issues with elevator trim not working. And for VFR/sightseeing, the scenery is only good because I’ve downloaded/installed the (free) Ortho4XP files for the states I fly (but the scenery is more realistic than Prepar3d with $50 of paid scenery).
For me, unless the initial reviews are horrid, FS2020 is a “must buy” for me. I’m sure there will be ways the others are better - flight model, ATC, flight planning…don’t know. But for the price point, I’m very eager to try it out, and FOR ME scenery is a big deal.