According to the latest Letter from the Producer, Final Fantasy XIV: A Realm Reborn is likely to enter its alpha testing cycle towards the end of this month. In addition, players wishing to continue playing the current version of the game will be allowed to do so even after the v2.0 goes live later this year. The caveat is that if log ins drop below 30%, the servers will be shut down.
However, we’re going to take a look at the login numbers at the end of each month. In the event that numbers drop below 30%, we’ll take the servers down again, and decide where to go from there. Expect more details on when the servers will be back online after everything’s been shut down. But for now, go and have as much fun as you can before November 1
Read the full Producer's Letter on the Final Fantasy XIV site.