It won't. Not a new edition of D&D. And it will. Now let me explain the dichotomy:
If WIZARDS OF THE COAST is smart enough - and I think they've learned how to handle things smartly, now - what they will do is provide outlets for people, like me, like others, who want to play AD&D. Or original D&D. Or 2e, 3e, 4e, and the various stripes of Basic D&D.
Most gamers I know are smart enough to know good behavior and reward it accordingly. I know that I myself won't drop AD&D for D&Dn. This time around WIZARDS OF THE COAST doesn't want that.
So far as we can tell there are no crazy ad campaigns on the horizon telling us old D&D sucks and is bad and we're bad for playing it. There's nothing lurking back behind the curtain, no dirty tricks. I do not know if WIZARDS OF THE COAST are planning to re-release, in a permanent fashion, older versions of D&D. As I said though I think they're smart, and I think they will. Probably through DDi, so they can control the sales a little bit better*, but it will get back out there. When people ask "What D&D is 'official'?" WIZARDS can respond, simply "All D&D is official. D&Dn is what's current."
In doing this, WIZARDS OF THE COAST will have create huge goodwill amongst D&D players. They will have become the Great Mediator in the cyclic and wasteful and hilariously stupidly hateful "edition wars".
This will make D&Dn a success. Goodwill will pay off, even the old guard guys like me will at the very least reward that with a try-and-play and wind up with an "only-occasionally" played copy of D&Dn on their shelves. I want D&Dn to become my second favorite RPG. A close, close, close second. Like, "hm, flip a coin, will I run AD&D for this or will I use the new D&D?" There are things I know the new D&D can never be - and that's OK. But what it can do - what WIZARDS OF THE COAST must make it do is be the "ambassador of goodwill Edition". They can't just pay lip service to the idea of "play any edition you like!" That promise must have teeth. If it does...then D&Dn will succeed.
I hope that makes sense.