While the OGL may be great for players, its better for Hasbro. Hasbro can, essentially, do nothing and 3rd party support will keep up the sales of the PHB for years to come.
D&D is a license, just like GIjOE. Its not neccessary for D&D game books to make money for the D&D license to be successful. Novels, movies, TV shows, family boardgames all have better profit margins than RPGs. Hasbro can keep the D&D license intact while farming out all the dirty, not-so-profitable RPG work to contractors (as in the case of the game world "contest" which is simply a request for submissions). Even the sale of the retail group and magazines makes sense. I wouldn't be suprised if Hasbro ended up with four or less permanent RPG employees.
Think about it, with the ELH released, there isn't all that much left to do for D&D 3e. New books will continue to have smaller and smaller audiences. A fourth edition would require too much investment so they'll milk 3e for eight years to come.
I think D&D is "safe" for the forseeable future.
Aaron