That may be the case, but the game has an almost 50 year history, and part of that history is saying "it will be compatible!" each and every time. And, in the case of Essentials, it was. So it's not without precedent. But that's not what usually happens.
And who knows if the people who are saying it are actually in the position to make that call? I don't know Crawford, but I have friends who do, and he is pretty well thought of. He's a solid gamer. But WotC isn't being run by gamers at the moment. The recent kerfuffle proves that and no one who was making those calls has been fired.
So when we come to the bottom of it all: we have WotC saying it will be compatible and if you believe them, then I guess there's no point in this thread. I don't believe that. I'm going based on what has been said in the past and what has happened before, and I could be quite wrong. I think, however, that just saying "this time will be different," is just as reaching as what I'm saying, since people have said the same exact thing before as far as what would happen that time. I don't know if even the people who are talking now about what will happen actually do know what will really happen.