This month, they have published a patent application for a visual effect system that allows theme park guests to see 3D augmented reality imagery without glasses.
The system "allows a viewer with eyes positioned at the left and right eye box positions to perceive a three-dimensional (3D) virtual object in the physical space concurrently with light from physical objects or scenery in the physical space," according to the patent filing.
In other words, if I can describe this correctly, instead of projecting left and right images that you would see through a pair of glasses as a 3D image, the two images would be projected on a transparent surface in front of your ride vehicle - that would do the job of the glasses in bringing the two images together as one, 3D image.