Some people have been able to figure this out, but what led to this discovery was actually Wratheon's 5.4 Legendary Quest chain. The island is located off the southeast corner of Jade Forest. For edification sake here are the quests in question:
http://ptr.wowdb.com/quests/33087-me...ack-at-the-inn - Initial quest upon 5.4's release.
http://ptr.wowdb.com/quests/33088-a-timeless-discovery - Going to Timeless Isle
http://ptr.wowdb.com/quests/33098-se...-timeless-isle - Collecting 50 Timeless Coins that drop from anything and everything on the isle
http://ptr.wowdb.com/quests/33100-the-emperors-way - Killing the four Celestials on the isle. The Celestials are considered world bosses
http://ptr.wowdb.com/quests/33104-a-pandaren-legend - Augmenting your ilvl 600 cloak
http://ptr.wowdb.com/quests/33105-ju...e-black-prince - Killing Garrosh
So I hoped onto the PTR and located the general location of the island
However, similar to how Blizzard locked areas during Beta, you couldn't quite get there yet. If you got too close, you were ported back to the Jade Forest Mainland. Due to the distance between the mainland and the island, there is an area where you will get fatigued. Once near the island there is a SLIVER of an area where you can move around a little bit without triggering the porting and not getting fatigued. I took two screenshots to show the depth and magnitude of the island. If someone can get better shots please supply.
TOM_RUS was able to Hunter Eagle Eye into the island and came up with a nice set of images, including showing the Celestials
TOM also posted a video of what to expect on the isle.