I think you are generally correct. New themes are still being created, but certainly not at the fast-paced rate they were done about 5 years ago. There’s still a place for themes, just not as high a demand as previously. My guess is themes will continue for a number of years to come as they serve a great purpose for several folks.
OTOH Foundry and Foundation have really expanded what intermediate and advanced users can do. So this is also not a surprise. This has been a great development for RW.
There’s a small but growing tertiary market: people who make projects with Foundation or Foundry. In turn this allows users to more quickly understand and use nicely designed projects that take advantage of these two themeless themes. I’d guess this market will continue to grow.
Stack development still seems very strong. So in general it seems RW still has a strong base of users.