D&D Online in a nutshell:
You buy the game, you play it for a year, then the new WotC ruleset gets published. So what do Atari do, update the ruleset for the existing game? No of course not, they release a new one and you get charged all over again. Good fun!
I've yet to see a mmorpg publisher that genuinely has any concern that isn't directly related to profit. That's why things like NWN2 will always rule.