If you are taking this strategy in game design, you had better have lower price points on products, which they are going to. Good times ahead for D&D.
This is Games Workshop's strategy. Rules every x number of years, with a rotating schedule of codices (splat books, or class books). They tried the lower price point for smaller releases track, and the fan base howled at the loss of background information. If WotC is taking their cue (at least on the rules side of things), I expect they're smart enough to jump a step and stick with expensive books full of content.
I like the idea of an evolutionary system with a core set of rules and modular bits, but [EW]I wish they'd done it with a version of the game I'd bought into.[/EW] Hopefully they don't fall into the release trap where less popular choices are stuck with older versions of the rules. Somewhere down the line people may find themselves at a table with 6e rules, a 6e fighter and wizard, 5e cleric, an Essentials thief and a 4e monk.