Planned rules/supplement/revise/repeat is the current model but that can't last much longer. Either the revisions aren't radical enough to warrant change in the eyes of the consumer or they go way too far and split the player base.
Plus the company stands to its customers like a virus to its host. It just keeps draining their resources until they're wiped out and then moves on to the next one. I don't think such a scorched earth policy has ever been good business in any industry.
It seems to me that with the traditional model (selling core books, supplements, adventures and accessories), there are two ways you can go: one is the Virus model above, where you get a small, solid group of hosts and bleed them dry over a period of years until they can't take it anymore and then you get another group of them, wash/rinse/repeat. The other is what you might call the Gygax model, which is to produce a core set of rules so good that it will only require small revision over time, and all revisions are cross compatible. To your core group of early adopters you sell a bunch of adventures, magazines and the occasional rules supplement. But in the main you focus on taking your excellent core product and constantly expanding your customer base by bringing in throngs of new customers.