Square Enix announced that you can now pre-order the Heavensword expansion for Final Fantasy XIV. On top of that, they also revealed the contents of a Collector's Edition for the expansion.
The Collector’s Edition package features:

• “Dragonsong War” Exclusive Box featuring art by famed Final Fantasy artist Yoshitaka Amano
• Expertly-Crafted Dragon Mount Figure
• Final Fantasy XIV: Heavensward Art Book
• Final Fantasy XIV: A Realm Reborn Movie Blu-ray Disc
• In-game items including a Flying Griffin Mount - Dark Knight Cecil-themed Baron Helm - Wind-Up Kain minion - Fantasia

Additionally, players who pre-order Heavensward will receive exclusive bonuses including:

• In-game items: Baron Circlet - Baron Earrings - Chocobo Chick Courier minion
• Early access to the Heavensward starting June 19, 2015.

Alongside versions available for PlayStation 4 computer entertainment system, PlayStation 3 computer entertainment system and Windows PC, a Mac OS version of the title will be available for the first time exclusively as a digital all-in-one bundle.

Players will also be able to pre-order the digital versions of each edition which will grant players access to the pre-order bonuses. Additionally, a digital upgrade option will be available for players that want to upgrade to the Collector’s Edition for the in-game bonus items, but forego the physical items.

Final Fantasy XIV: Heavensward Collector’s Edition is available for pre-order on disc for $129.99 and digitally for $59.99. The standard edition is available for $39.99 and the all-in-one bundle is available for $59.99.

As noted, the early access period will begin on June 19. If you can't access the game at that point, the non-early access release of the expansion will be on June 23. The expansion includes new story, a new level cap of 60, a new playable race, new dungeons and raids, new mounts, and more.