No, I find the notion of a 5.1 or 5.2 just as distasteful as a 5.5. Perhaps even more so. Again- I absolutely don't want to feel pressure to buy new books just to get a few twiddles in my game. Not at all. My desire level for that is well below zero.
WotC has repeatedly made plain that they don't want to publish books for niche parts of the market. They've explicitly stated that they want to write and publish material that almost everyone wants. I don't want what you describe, and my sense is that my attitude is, if not prevalent, at least common enough that such a book wouldn't sell well enough to justify writing.
The thing is, the core books are core. You need them to have a complete game. And I have them. I actually own two copies of each- one for my place, one for my gf's house. I had no problem buying an extra copy of them. But I wasn't forced or pressured to; it was a choice I made to make it more convenient to run games from multiple places. A PH Revised is a different beast entirely- if you don't get it, your game is no longer current, but if the changes are minor, fiddly, errata-based stuff, why not just keep doing what they're doing and simply incorporate those changes into new printings while making them (errata) freely available online? OTOH if they're significant, then we really are looking at a revised edition, in which case, unless the changes really improve the game without invalidating older material (and that's a very tall order indeed), I'm not interested.
I would much rather see a full on new edition than a 5.1 or 5.5. And I see no need for a full on new edition at this point- 5e is working fine (at least for my groups).
It seems that you are in the vocal minority. But as far as 5.1/2 goes, I would guess that it is a very small one. As the number goes up to 5.5, it gets larger (and louder).
But as you said, WotC wants to publish books that "almost everyone wants." Let's emphasize
almost, because there is simply no pleasing everyone. Whatever WotC publishes, they're going to upset someone--even if they publish or re-publish every possible configuration of the game.
I cannot disagree with your opinion for you, but I disagree that it extends beyond a small group that isn't in the "almost everyone." In my mind it is not only reasonable, but preferable, that they update the core rulebooks every decade or so, if only as a re-skinning and errata. I mean, if only because a physical book gets used a lot in ten years of gaming, and it might be nice to spend money on a copy with errata, some new art, and a few new bells and whistles.
Here's a question: Let's say they do what I think they will and should do, and publish a 50th anniversary set that includes errata, a few tweaks and clarifications to stuff like monster stats, spells and magic items, and maybe a new class or two, and some new art and resources. No significant mechanical changes, so fully backwards compatible, the only choices to be made are stuff like: do you want to used the clarified
wish spell or not, which version of the ranger or death knight, do you include the warlord in your campaign or not? Etc...meaning, nothing other than what we're already doing with
Xanathar's and Unearthed Arcana.
But here's the kicker, or addition to my previous scenario: For the additions (e.g. new or altered classes) they offer free PDFs, so you don't have to buy the new books to use them. Would that bother you?