Cant really think of a date. Im hoping jan-march next year. One thing is certain though. For every mon that the game is down they lose sub money (not that its an astonomical amount compared to say WoW). They also lose potemtial sub money for those wanting to pick it up at launch. They also have to pay the dev teams' salaries and pay for promotions and thing of that nature.

If SE is smart they planned ahead so as not to have an extreme amount of downtime. Im sure they also dont want people getting too attached to other games and MMOs. For alot of people just a month or two is enough time to forget about ARR and move on.