What I've found interesting about this downtime is that, if substantial, it gives players a time to get their "fix" elsewhere, and perhaps develop an attachment during said downtime there instead. Be it FFXI (imagine if the new expansion pack came out before ARR comes back online), another company's MMO, or even just offline games, not only will SE be trying to attract new players, but they'll have to work towards convincing those that have spent their time gaming elsewhere during the downtime to return before they grow attached to another game.