I think the "edition-less" nature of D&D is more real than folks are giving it credit as being.
When 3E came out, there was no question that it was a new game compared to 2E a few years ago. It was broadly compatible -- with work, and some parts were a lot more compatible than others -- but no one would be confused which edition they were reading, with two books side by side.
4E, if anything, was an even bigger break with 3E.
And then 5E broke back the other direction.
The "edition-less" D&D means they're going to stop doing that. The basic 5E chassis will remain the same for the foreseeable future, even if there are updates. But it's a system with six stats, a d20 resolution system where high is better for almost everything, NPCs are built differently than PCs and advantage/disadvantage replaces nearly all bonuses and penalties.
If they successfully manage it, being able to pick up the 2034 PHB and run Hoard of the Dragon Queen with it, without any special conversion notes, is a very big deal, both for Hasbro and for gamers in general.