It seems we were right! According to the Disneyland Annual Passholder website:
Enter the Toy Story Mania! Annual Passholder Sneak Peek opportunity drawing to be one of the very first Disney’s California Adventure® Park Guests to ride Toy Story Mania! Take advantage of this exciting chance to be a part of Disneyland® Resort history.
For more information & to sign up for this “sneak peak” of Toy Story Mania, click here!