Square-Enix is running beta tests over weekends in April. The focus of phase 2 is on the city-state of Gridania, Gamepad support for the PC, Chocobo mounts, and full active time events. It's not too late to sign up for the beta, either.
When Final Fantasy XIV hits closed beta phase 3, the team will add in the PlayStation 3 version and a "huge amount" of additional content. Specific details and timing of phase 3 have yet to be announced.
[Source: Square-Enix press release]