Sure. But I think that is, if not completely orthogonal to "supplements vs core", at least very complex in its relationship to it.WotC sells a lot more material than just RPG content.
For instance, one reason given on this thread in favour of "supplements over core" is that this extends the lifecycle of the edition. But from the point of view of non-RPG monetisation of the D&D brand, edition cycles are not all that crucial. People who are paying money for D&D boardgames or movies or coffee mugs don't particularly care what permutation of mechanics those who play the RPG are engaging with. (Or, if they do, because they are all themsevels actual or about-to-be RPGers, then the plan to expand the brand hasn't really worked.)
And given that edition cycling seems to be one way in which WotC gets a degree of mainstream press (it happened with 4e too, as best I recall, and presumably with 3E also) then edition cycling might actually support broader promotion and monetisation of the brand.
I think you are right, and I actually think this is the biggest point of collision between the incentives of a commercial RPG publisher, and the good of the RPG hobby. (On this point I'm basically an unreconstructed Forge-ist.)Perhaps it might be better to appeal to the "I like to read" players out there. A supplement is tied strongly to a theme and thus becomes more obvious where it should fit.
My view is that the selling of other peoples' play experience, or of their fiction, as "gaming supplements", encourages bad GMing and bad play experiences. (Railroading and player passivity.) The game should be providing players and GMs with the tools and techniques to make their own fiction.
That's why I've always been puzzled by the criticism of 4e books as not being a good read. They're not novels, they're lists of game elements. I do enjoy reading my 4e books, but not because they tell me a story: rather, they make me imagine ways to get those elements into play in way that might make for a fun game. (That's why I've never read through the seeker or warden powers - thsee classes has never appealed to me as elements of a game.)
But from WotC's point of view, I can absolutely see that if they want to sell material, they need to sell it as reading material rather than gaming material. (Or as reading material loosely presented as gaming material.) Thematic supplements would work well along those lines.
Not if what the fans want is not much stuff. Luckily for WotC I think many D&D fans actually want more stuff than they typically say they want, although I think Hussar is right that the way in which it is presented and made appealing is quite important.If the fans are getting what they want, then in the long term Wizards wins too.