They tried the D&D (no qualifier) thing with both 3e and 4e. It didn't stick.
I've been told this twice recently. It's just plain wrong.
The cover of the /4e PHB says "Dungeons and Dragons" in big letters. Which version of it do you have?


As does the /3e addition by the looks of this.
So - show us a book with the brand name of the game being D&D for /3e or /4e.
Note: That is different from a D&D logo existing which is also used to mark WoTC products.