Whisperfoot said:
... What I would like to see are more Spelljammers, Eberrons, Darksuns, and Midnights. What I would like to see less of are the Greyhawks, the Middle Earths, and Krynns - I love them to death, but is there really any new ground to cover there?
(Putting Krynn in the same category as Middle-earth is annoying, but whatever

..)
The fact of the matter is that most people who play DnD are not looking for the "exotic". Most just want your "Conan-meets-Gandalf" kinda game. They play once every week at most -- probably less, given how much damn time it takes to prepare 3.x adventures, etc. -- and are happy to play McGruff the "grumpy Scott/Dwarf"; Cleverardo the "cunning and charming Elvish thief"; etc. Stereotypes reign supreme in most "Sunday evening" games.
In short, I agree with your claim that DM-products are the ones that will last, but disagree with your claim that "unusual" settings are the way to go.
So this gets to the "meat-and-potatoes" point of your post, which is correct: in the long-run, the things that will sell, are the "campaign-maintainers", that is, the tools (namely, campaign settings and adventures) that enable a GM to keep his/her campaign going without too much effort. But I am not sure that "exotic" is necessarily the way to go. I mean, how many "Eberrons", "Steampunks," and "Iron Kingdoms" can the market handle?
Okay, I am rambling. But I suspect that some percentage above 60 of all gamers would be happy with a minimal Greyhawk setting and monthly adventures from Dungeon.
The prognosis is grim. The RPG market is diminishing.
But frankly, I have no stats to back any of this up.
Nevertheless: you heard it here first!
Seriously, 20 years from now: NO Rpg industry, just fan-supported material. I kid you not. Start updating your vitae now. :\