This is old news, we heard about this during our interview at E3-

GE: Speaking of Beta, will there be downtime between current game and 2.0?

Yoshida: What’s going to happen is that after the current version is finished and storyline over, the servers will go down and the 2.0 beta will start up. We want to make sure we don’t make the same mistake as before, and want to be sure we have enough time not only for the beta test but also to get feedback from the players and leave enough time to implement that feedback. Also, keep in mind that transferring the characters to the new servers and systems could take up to a month. So that process will be running while the beta test is in place. There can’t be a launch immediately after the current servers are shut down.
Keep in mind, the month is only for transferring character data from 1.xx to 2.0. HOWEVER, they are still using the beta to gather feedback and this time they want to make sure they do the beta process correctly and act on all the feedback. So really we're looking at the game being down for more like 2, maybe 3 months while they get feedback and make changes in addition to transferring the character data.