IMO, its great to see other company's make the R&D projects public. Google and others do highlight that such projects are research and if the public wants to, can buy them and join the experiment, such as Google Glasses. Some projects won't be released commercially, others will.
Apple are a serious hardware company, not a playground of experiments and abandoned "projects". I am very sure they have prototypes of experimental VR mechanisms which they've considered, but, unlike various other naive companies, they are prudent enough to keep them secret and locked inside a cabinet of the R&D team at Apple, knowing they were only experimental projects, not release them as products which they expect people to take seriously.