Who exactly is it confusing for. If you are a new players, who has never played before, you just buy the book they have at target or amazon.
If you are an existing player, you should be aware that a new revision is coming out, and you aren't going to be confused by them.
Dude, people buy stuff second hand and it's not like there won't be stock of these PHBs out there. They might borrow an old PHB from someone they know plays the game because you're just saying the 5E Player's Handbook. The idea that "New players will just buy the new one" misses that these are effectively called the same thing and only older players will know. If you are new and try to buy one cheap, second-hand, or simply borrow it, you'll be getting something that is not the same as the older one.
And I don't see how that's any less confusing than putting a "5.5E" on it. If you're new, you're just buying the one off Amazon, right? If you're an older player, of course you know what you're getting. As an argument for clarity, it is a
terrible one.
I guess then we drastically disagree about how incompatible the two PHBs are
Given that the Warlock is drastically different, there's huge debate on how to implement Wildshape, and other such things (Oh God, Weapon Masteries and 2014 Martials

, new Martials and old feats...), I'm not sure how you can't create some real disruption within the community itself if you allow both books to be used. I don't see how you can nerf some classes and expect the older versions not to get used without a GM just saying "No".
But calling it 5.5 or another edition is not telling you what you get. It's not a new edition of the game. It is not a clean break.
It tells you you have the most recent revision of the rules, which is more than just calling the new book the same thing and hoping that the market will clear things up.
I predict that the 2024 PH will likely just say Player's Handbook on the cover, and on the back cover likely have a blurb providing a clarifying statement that it is an updated revision celebrating the anniversary of the game, like the 2014 PH says that it is for the fifth edition of the game.
The physical way to differentiate it is that the cover is going to have completely different art.
The way they will differentiate it in text, like on a list, will have the year designation, like "Player's Handbook (2024)"
The 2014 Core books will stop being printed, (maybe they stopped printing already), and dwindle away out of the market over time, bought by people who decide they would rather stick with the 2014 rules. There will come a time where people can only buy the 2014 books, used.
The 2024 books will become the new norm. And some people will still complain, and new players who enjoy the new books won't "get it" because they cut their teeth on the 2024 books and love them as the books of their generation... just like many here have fond memories of their favorite early edition.
IMHO.
I mean, if we are going to rely on those cues, that's just an edition change without the number. What the number does is make clear this is something different from the original.
At the very least, this does not create clarity. You're just going to have 5E Fire Giant versus 5E Beholder (or whatever they put on the cover... eh, let's be honest, it's probably going to be a Red Dragon

), which is going be a more exclusive, opaque nomenclature compared to just saying 5.5E or "Revised" or whatever.