Again, I have no doubt that 4E is selling a bunch of books, that's not my beef. More sales than the "last couple years" of 3.5 material, easy to believe.
But re: "breaking all sorts of records" (per post #31), you just quoted Joseph Goodman saying the following, which I count as contradicting that claim:
Maybe he's misinformed? It's just his gut feeling, I don't know what he did around 3E and what he does now. I don't like to assume that anyone is lying, so I would say WotC is pretty sure about their print runs for 3E, 3.5 and 4E, and I wouldn't be surprised if individual distributors aren't so much aware of it.
Though I am not sure - was he talking about the 4E core rulebooks or was he talking about the Goodman Games products launched? (I am not familiar enough with Goodman Games to know what they did during the 3E launch and what they are doing now...)
First, all I will say regarding promises made before 4e fully came out, is that ze game did not remain ze same
It did remain the same for some values of sameyness. OD&D, AD&D and D&D 3E all were the same and they were all different, too. The game still always remains the same with its dungeon exploring focus and its essential classes and races... (as opposed to Core classes and races, which did change over time)
Ignoring the issues of sales and all that nonesense, instead I'll touch on this idea of "sales = quality." Good lord, this is a frightening idea - scratch that, terrifying idea - in a world where Twilight sells well and the Wayans Brothers are still able to make movies.
You know, the trick is - there are different types of qualities. To go in the generic food analogy thing: Fast Food for example has the quality of being fast and easy to get. It might not be as healthy or as refined as other options, but if you want your food fast, you go to Burger King or McDonalds.
A fish restaurant might make the best fish in the world, but if you want a noodle salad, it's not getting a sale from you.
So yes, "sales = quality", for the type of quality people want. (Notice: Type does not mean "degree" or "level")
D&D always had the quality and the qualities a lot of people wanted. If it ceases to do so, the value of the D&D brand will diminish, and it won't sell as good as it used to. If AD&D, D&D 3E or D&D 4E would have been bad games, D&D would no longer bring in the same amount of customers and cease being a guarantee for good sales.