Honestly, there is a problem-- 2 conflicting things:
1. D&D needs to make money to thrive.
2. D&D doesn't require many editions or books to play a good game.
Many players will avoid new editions, or at the very least, be reluctant to buy them, because the game really is fine the way it is. Heck 1st ed was pretty much fine the way it was: a few house rules and you got one heck of a game. With 3rd ed (and now 3.5) its pretty much as good as it gonna get.
Sure you can keep tweaking the rules...but really this isn't playstation and x-box we are talking about...the technology isn't gonna get much better--its a book! We are not discovering new science to make role playing better, nor are we discovering new ways to print books or pictures. Really, until we somehow update the technology of roleplaying, there really is no need for new editions. Bottom line, D&D had three editions (i dont count the revised 3.5, where they just tweaked it). The first, technology and art in game material was in its infancy: black and white crappy art, crappy binding, boring layouts, and so on. 2nd ed was slightly better. 3e showed us the best: good art, good layouts, good text, good books. But really, where do we go from here? Until we discover something new, or at least enter a new generation with even higher expectations, there is no point to releasing 4e...except to make money.
But will it do that?
ok 3.5 worked. Sort of. I bought it. It was indeed better than 3rd ed. It was mostly compatible with 3e. Did everyone buy it? No. Am I as interested in it as I was when 3e came out? No. Heck, I rarely buy new books anymore because a lot of it is just the same old stuff "updated" to 3.5. Gamers are fairly intelligent people...most dont require another book to aid in translating from a half edition below. Heck I still translate my 1st ed stuff to 3.5. I have probably around 1000 lbs of D&D books (no exagerating). I got rid of the stuff I would never use again. 1/4 of my collection is 1st ed, 1/2 is 2nd ed, and 1/4 is 3rd ed. I have 5 books that are 3.5. If fourth ed came out, I might buy a couple...maybe, if they had something my other books did not...not very likely.
In sumary of this ramble, most D&D gamers really don't want a new edition...ever (or until it will actually make a difference...holographic interactive graphics perhaps?). Wizards/hasbro will give us one anyway...probably sooner than later. Some of us will buy it. It will prolly be better than 3.5. It wont sell well, buit we'll still see the equivalent of "the rangers hanbook" and "Gnomes & Halflings" come out anyway. I dont really know where it will head, but it looks dismal.
Personally, I think perhaps D&D has met its final incarnation for now. Its not magic the gathering, pokemon...its more of a chess or monopoly. Sure you can put out new editions...but you not really adding anything thrilling anymore. I would like to see it left alone for another decade or so.
I really do ramble on and on.
Ember