No. I'm not going to slog through all the threads and pages looking for the posters who have been telling me that it will be fine playing the two versions of the game simultaneously, because the new classes will be balanced with the old ones so one edition's classes won't be more powerful than the others. I'm certain that
@Parmandur was one of them, but there have been several.
If they aren't balanced, though, then WotC is wrong about backwards compatibility. As I pointed out to someone else, I COULD use the 3.5 version of wish in a 2014 or 2024 game. It's not going to cause the game to melt down and stop if I do that and the rules are similar enough to be workable. Unbalanced, but workable.