In the upper right corner of my blog you will see this
I have to wonder if Dragonlance/Forgotten Realms approach to setting supplements is the way to go. Why not release a series of more limited setting designed to dovetail into existing D&D campaigns? Give them a loose background that ties them into the Forgotten Realms/Greyhawk/Dragonlance/etc but your meat and potatoes products are the mini-settings of 200 miles by 100 miles.
Yes I know I am tooting my own horn here considering my work on Blackmarsh, Wild North, and both Points of Lights. But think about it, even for Forgotten Realms, Harn, Glorantha, Tekemul, and other setting with a long publishing history the amount of written details barely fill what one could write about a real country like France, China, or Mexico. The settings I mentioned have a ENTIRE WORLD of possibilities unexplored and unwritten about. This especially true of kitchen sink settings like the Forgotten Realms. Moreso you are not limited in time as well. You can make mini-settings set in the past as well to take advantage of interesting circumstances.
The tie-in novels can continue the way they do now. Organize play material is not changed. The only thing that changes is that for your RPG audience you sell them Blackmarsh size or Nentil's Vale size chunks of the setting. If you need to explain the background of the setting you get your novel division to release the Gazeeteer of the Forgotten Realms just like Martin is releasing an Westeros Atlas. Or Kurtz released the Deryni Encyclopedia. If you want to adapt your generic genre RPG to the published setting then release a Majestic Wilderlands style supplement that focuses on that task with a short overview of the background. The idea here is to make the RPG product line modular to better serve how referees actually run their campaigns.
I want to close with that detailed settings like Glorantha, Harn, Tekemul are not bad. If an author has a specific vision and executes it well the result can make for a memorable RPG experience. But if you want as broad an audience as possible then a different approach is called for.