We've known for awhile that WotC has consciously taken a minimalist approach to splats (i.e. crunch-focused books); I don't see why they would change that approach.
I tend to believe that crunch minimalism (relative to the last few editions) is part of 5E's runaway success. Maybe not the main reason, but certainly an important secondary one.
Do you remember that talk in 2009ish about D&D needing an easier "on-ramp" for new players? That lead to Essentials, although for 4E it was too little/late, and/or didn't address other problems. But they took that basic idea and streamlined 5E, then decided to put out splat books on a slow drip rather than a deluge, which they seemingly rightfully believed would make the whole game less intimidating for new players.
And, of course, the focus of 5E has been on story and worlds, not customization and endless options like 3.5 or Pathfinder. That is even more central to the edition's success, and will continue to be the "spine" of the foreseeable future.
5E has a huge and diverse fan base, probably the bulk of whom are what might be called "casual players." It is no longer carried by a diehard core, who generally like more over less in terms of supplement options. This is not to say that the diehard core isn't an important component, just as DMs have always made up a sizable proportion of sales as they tend to buy a lot more books than casual players.
Fewer splats also means a less wobbly game, with fewer broken parts. A revised version at ten years makes perfect sense: it allows WotC to clean up the fiddly bits, and fix at least some of the broken parts. It also allows them to do a "micro-reset" with crunch.
One question I have is if we're going to see a similar player's crunch book to Monsters of the Multiverse; where that book essentially replaces Volo's and/or Mordenkainen's, such a hypothetical player's splat would do the same for Xanathar's and Tasha's, with some elements folded into the revised PHB itself).
And if they do that, will it be in 2023 to preview 5.5, or in 2025, to be the first splat for the revised core? I could see them going either way.