It's interesting how this discussion has evolved over time. I've said that discussion of editions really depends on what's changing. As we've seen the playtests come out, I think we have an idea of where things are going, but it may change of course depending on where Wizards wants to go with it.
From my perspective, this is a ".5" edition. I'd say it's fairly comparable to 3.5 where you had the same underlying systems but classes and spells changed significantly. You needed the 3.5 books to play a wizard because the spells had major changes to them, as did many of the classes. I've looked over the classes that I play and they are ... really different. I play complex characters so they are spell casters, which are pretty different. I build a lot of warlock into them and that's a very different class at the moment.
I think what Wizards would like to do is have it be an "Essentials" edition. If you didn't play 4E, Essentials presented new character classes that you could play along side existing 4E characters. We had a player that wanted a simple character, so they played a Slayer, which was a fighter variation. You could have a classic 4E fighter in the game right alongside one. Or a "thief" (the Essentials Rogue) right alongside a classic Rogue. That ... doesn't seem to be the mentality they are going with, so the classes will have the same name, and have varying levels of differences between the new and the old. That's why I'd call it a .5.
And there's nothing wrong with a .5 edition update! I was wondering if they were going to change the underlying game mechanics or not, which I think is sort of a pre-req for a "6E" update. I just wish that Crawford would just stay out of the "what edition is it?" discussions, since it usually just ends up creating discussions like this one.
Just an aside, with an explanation for why I think he's doing this: a .5 edition really needs you to buy the new books (if you're not going exclusively digital) so explaining that means that you'd have a lot of people not buying product until the next edition. I know I'm not. But I wasn't exactly buying Wizard's products beforehand. What I am affected by is Paizo's "revised" edition. That is a similar situation, and it means I'm not buying their books or APs until revised comes out, which actually means something. I have been buying their stuff.
So ... we don't really know what the new edition will bring, but in my opinion from the playtests, it looks like a .5 Edition.