The company has announced two new promotional campaigns, the first of which is aimed at players who have paid for at least 90 days of sub time since January 6th, 2012. You should be getting an email from Square if you're eligible, and you'll receive a discount on your monthly sub ($9.99 for 30 days) as well as 40 playable character slots on your account (with a maximum of eight per world).
Legacy members will also get an exclusive chocobo mount with version 2.0 as well as the option to have their names listed in the update's credits.
Square's second announcement concerns the Welcome Back Campaign, which is intended to stoke the interest of former players with inactive service accounts. Eorzean ex-patriots can come back for free between May 9th and May 20th. During the 10-day trial, you can take part in the "once-in-a-lifetime" Seventh Umbral Era content and experience the new job system and inn room updates. Finally, Naoki Yoshida has published a new producer's letter that expounds on the campaigns as well as the game's future.
[Thanks to William for the tip!]