Some of you may remember the patent Nintendo had for detachable controllers that use IR technology, which could be made extremely cheaply with no electronic parts. Well, the recently leaked documents say that the right Joy-Con's IR camera will be used for just that purpose. From the recently leaked documents in regards to the IR camera:
Attachments made only of plastic with no electric parts can be created if materials such as recursive retroreflectors are used."
The patent had also said these controllers could include NFC tags to send basic info to the system. It just so happens that the right Joy-Con also has the NFC reader.
I think this means we will see what are essentially hybrids of Amiibo and functioning controllers that attach to the right Joy-Con.