In the August 8 Live Letter, Yoshi-P announced the dates for the next beta test as well as early access. Players who participated in the most recent beta test (phase 3) will be able to start one day earlier. Here is the relevant info:

"Beta Test phase 4 will run from August 17-19. Those who participated in the Beta Test phase 3 will be able to participate from August 16th. Early access will run from August 24th until the 26th with official service begins on August 27th, but the servers won't go down after Early Access, so you'll be able to play non-stop from August 24th."

You can also check out the Live Letter summary over at the Lodestone:
http://forum.square-enix.com/ffxiv/threads/62880-Letter-from-the-Producer-LIVE-Part-VIII-Q-A-Updates

I'm more excited to start the game than ever before, if that's even possible! I'm not sure if having a set-date makes waiting easier.