They’ve been posting weekly development updates. Here’s one from last week that has a roadmap based on feedback from the beta - https://www.flightsimulator.com/august-13th-2020-development.... It definitely seems this will be more of a service model.

Because it's a different kind of game with a different kind of audience. Simmers are accustomed to paying for additional content, and this is a much more stable and lucrative strategy than abandoning the title. Just look at Paradox.