the online subscription model is the only thing that could change the inevitable short life-span of editions... wotc won't have to cram more splat into the game (i.e. publish a new book every month) until its unplayable if they can just get subscription $'s every month from everyone who plays
I imagine they are thinking quite a bit about it.
The fundamental problem of D&D from a business perspective is that the more you (the customer) get into the game, the more time you spend on it, and the better you are at it, the less money you are likely to spend on it.
Also, the better the quality of product that is out there, the more it will stand the test of time, and the less likely anyone who owns it is to buy a new version.
I don't know that anyone will ever be able to change those things, which is why the game will always be tough to make money with.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.