It's hard to argue with their current success, and the factors that seem to have contributed to that success. Especially when compared to recent past editions, and the factors that contributed to those failings.
I mean, it seems like the release of Forgotten Realms and Dark Sun campaign books did little to help 4E's success. Why should they expect anything different now? Their books are doing just fine without providing a full on setting Realms book. They're slowly getting to different areas of the setting, and doing it while packaged with adventure paths.
The setting books they've done so far....Ravnica, Ebberon, and now Wildemount....all have a pretty strong reason for existing. Ravnica tapped into the Magic the Gathering fanbase. Wildemount does the same, but with the CR fanbase. Ebberon is the youngest of the "classic" D&D settings and the on with the lease amount of content, while also still having a vibe that is different than the kitchen sink approach used by the Forgotten Realms.
If these books do well, then I expect we'll continue to see setting books. But it's just going to be at a slow pace. They're not going to start cranking out more settings like crazy now. They're going to take a setting and look at what it has to offer to customers, and how wide the appeal will be. They then have to weight that against other settings and products to determine what's the best move at any time.
Part of what they seem to want to do is create an evergreen edition. To do that, they need to keep the slow and steady pace, and hope that the open game license and DMs Guild can help those who are looking for additional material at a faster pace.