MerricB said:I do not believe the "One System to Rule Them All" theory. It makes the assumption that the guys behind the OGL were really dumb, and believed that everyone would be satisfied with one system.
I direct you to this interview with Ryan Dancey, on the WotC website.
...and in particular, this quote (bolded for emphasis):
The logical conclusion says that reducing the "cost" to other people to publishing and supporting the core D&D game to zero should eventually drive support for all other game systems to the lowest level possible in the market, create customer resistance to the introduction of new systems, and the result of all that "support" redirected to the D&D game will be to steadily increase the number of people who play D&D, thus driving sales of the core books.