I think it's actually going to be far more confusing because you are going to have two different sets of designs for the same classes be viable at once, allowing players to choose between two rather differently-designed systems. You can say "Well, who will play the old stuff?" and I would say "More than you probably think".
Seriously, look at the debates we've had on this board alone: there are plenty of people who don't like the new designs and want things closer to the old stuff. Instead of saying "Well, you can play the older edition that is balanced around those conceits", you're now saying "Well, you can still use that old version at the table", thus completely negating the attempt to fix it by still outright allowing it with no changes. Don't like the 2024's version of the newly-balance druid? Well, time to go back to the 2014 druid with all its Circle of the Moon problems.
You can try and handwave the idea away, but the fact that people can just bring the old rules to the table if they don't like the new ones and try to play them is going to happen, and almost certainly more than you think. We've already seen some rough feedback for things like the Warlock. You don't think a bunch of people aren't just going to play the 2014 version?
Also, I find the conceit of "Everyone is going to buy the new rules" doesn't really play with the conceit of "You're going to cause a split in the community with a new edition", because I don't think a bunch of people are suddenly going to buy the rules only because they have a "5E" next to them. People are interested in the new rules because they are new, and I suspect that more people than you'd think would be up for an edition change right now. Instead, we're going to try and do a weird mixture of editions, where we have opposing designs competing. You're going to have people who ban old classes, or at least certain versions.