Still looking for DPB announcement but ..
TP -
These Evening Extra Magic Hours will certainly be right for the night owls, as they will take place from 11:00 p.m. until 1:00 a.m. Only Pandora – The World of Avatar will be open;
no other attractions in the park will be open to Guests.
Laughing Place -
With the excitement surrounding the opening of Pandora - the World of Avatar at Disney's Animal Kingdom, the park will now be open late — very late, if you're a Walt Disney World resort guest. Starting May 27th and going through July 4th, Animal Kingdom will offer nightly Extra Magic Hours from 11 p.m. to 1 a.m.,
although they will be limited only to the Pandora area.
Disney Parks Blog - not quite as clear -
And beginning May 27 (through July 4), guests staying in select Walt Disney World Resort hotels will have the opportunity to experience Pandora —
The World of Avatar with special nighttime Extra Magic Hours.
Guests of select Walt Disney World Resort hotels with a valid theme park admission can fly on the back of a banshee, navigate a mystical river and walk under floating mountains beyond regular park hours – from 11 p.m. until 1 a.m. This benefit is in addition to the Extra Magic Hours already available to you at Disney’s Animal Kingdom.