Streaming video will be a killer app of AR. Such a basic thing though is a huge challenge so far. There isn’t even a good AR display yet let alone everything else.
The short-term killer app of AR for consumers is probably a lot more mundane. I think things like heads-up displays on a car windshields or motorcycle helmet visor is a likely contender. But that could change if they get rid of the need for goggles. AR contact lenses could be pretty wild and a less anti-social.
There are a lot more opportunities for AR in commercial applications (like surgeons, technicians, etc...).