AndFirst off it is possible to play D&D (and any other rpg) with little or no actual roleplaying.
I admit I have not read ALL the replies in this thread, but this is essentially the 'problem' Why can Monopoly or Settlers make decent money? There is no continuous cost of development and massive staff. It is designed once, and pretty much all future sales are pure profit (minus production costs etc.).
So, this model could very well work from a Hasbro p.o.v., just treat it like any board game. Kill the WotC staff entire. Have a marketeer/product manager run the show on his/her own. When additional product is needed, source it out on a case-by-case basis. The core game never needs to change.
1) there have been actual Fantasy-based boardgames (Dungeon, Dark Tower, etc.) with various levels of success. None were world beaters.
2) as mentioned before, there are many RPGs out there that have changed their rules very litttle over their decades of existence and who have legions of happy fans, but by sheer force of business realities, are extremely unlikely to ever be The 800lb Gorilla of the RPG market.
A "Static Core" could work, and to me, one of the best things about a business model like that is it's much easier to support multiple game designs that way (in theory, at least).
If you do go with a "Static Core" design theory, you have to find something else to sell to keep your company afloat because you're not going to sell enough of one single game to make it. So, you might be able to sell D&D1, D&D2, D&D3, etc., each based on a revised & cleaned up version of a particular version of D&D...just like Habro sells more than just Monopoly.
But even that won't keep an RPG company afloat. Look at some of the "Static Core" games out there, like HERO or GURPS: despite needing only the core rulebooks to play, despite the stability of their rulesets, both games have a few editions and dozens of supplements.
So even though the rules are stable, you still get edition treadmills (though really, they're more like revisions) and you have to produce adventures and/or supplements that are well-written and provide utility to the end users.
Because if you don't, static core becomes stagnation which becomes going out of business...