You think there's enough hardcore D&D players to put someone at the top of NYT's best seller lists, repeatedly?
Yes.
Don't kid yourselves. Dungeons & Dragons (and especially the associated novels business) is one of the most reliable, steady publishing operations in the science fiction and fantasy field today.
It doesn't get nearly the critical reception other "mainstream" novels receive, but it doesn't need it, because it is swimming in money.
How many other companies can you think of that have an entire shelf in almost every Barnes & Noble in the country filled top to bottom with their products? In science fiction and fantasy?
The only one that is even close (and growing increasingly closer) is Games Workshop's Warhammer novel line, which is patterend entirely off the Wizards of the Coast (really TSR) business model.
--Erik