Before a full-on beta test, they want to create more "developer versions" like they featured at Gamescom in order to let players try out different sections of the game system. As an example, Tanaka says players tried Guildleve this time, but maybe next time would focus on the battle system more heavily. After that, they would consider opening up a beta that included the game as a whole. This is what they meant when they expressed their intention to have a prolonged beta process. They are going to use the time between now and release to really examine and test all aspects of the game.
If this is saying what I think it's saying, awesome.
Before this I was wondering what he could have meant when he talked about "giving everyone a chance to try" and "having something ready before 2010." 2009 would be too early for the full beta, but they wouldn't release a "demo" before the beta because the game could change significantly before release.
But if they combine the two into something like a "battle system beta," it suddenly makes sense. Now they can release a very controlled and restricted version of the game early on: something that will appease the fans while collecting valuable feedback they can use. And it's all done with the understanding that it's a beta, so no one should judge its flaws too harshly.
That's assuming that these mini-betas will be freely available to everyone. That might not be the case, but it sounds like what he was talking about in the earlier interviews.