Just a point here: WotC isn't working on a 6e. It's working in a 5.5e. Everything will be compatible to 5e material exactly in the same way 3.5 material were compatible with 3.0 material. Nothing new on this front. They said that this edition (5.5e is unofficial and oned&d has been scrapped) will be their last and will live in perpetuity but this is just laughable. By 2030 I bet there will be a 6th edition.
I think that's a farce though...some of the changes they want to bring are too drastically different. This 5.5e will be unrecognizable from 5e.
I don't think so. They can go as far as scraping all classes and subclasses and leaving in the game only three archetypes or whatever, but if they don't change the math the game remain the same. If I can play a 5e module with "new version" rules, then it's the same edition. Sure there will be some difference in powerscaling, as every time they add new rulebook like tasha or mordenakainen, but fights in 5e official modules has always been a mess. The first fight in descent into avernus is just ridicolous.
On the other hand I simply can't play a 3.5 module with 5e rules and the opposite. The math is just too different. A 3.5 cr1 monster would laugh in the face of 5e lv5 characters if not for the amount of hp.
