Final Fantasy XIV (FFXIV) will begin the first of four planned alpha tests for the A Realm Reborn update today and more changes are coming later this week as the Seventh Umbral Era event takes place in FFXIV. The final character saves for the current version of FFXIV will also take place on October 31st, 2012, but players can keep playing until the worlds come down on November 11th, 2012. At that time, the current version of the game will come to a close as FFXIV transitions to A Realm Reborn.
Additional details for the FFXIV: A Realm Reborn alpha and registration can be found here.
Source: Square Enix Press Release