On the controller would be very welcome. Would this do much to kill or harm the third party controller market tho? I suppose it would depend on how many games use it.
...Nintendo Switch already has a camera on the controller. Few games use it. Some games won't function without it.
Personally I'd just expect "more" of what we have now. More "Motion Cameras".
I think my dream would be:
Two on each Joy-Con, one on top, one on bottom, both in colour with an IR emitter. Tracks the room around you to help with spacial positioning. No sensor bar, no problem, it identifies the TV, or a picture on the wall, locks on and bam, super stable Gyro. Modern smartphone cameras are full colour but can also see in IR, so it could offer backwards compatibility with the IR Motion Camera's functions, use an IR emitter to see in the dark. Clip it on to a new accessory, and it becomes a remote control vehicle with a camera!
Personally I very much DON'T expect AR. That's the domain of mobile, and even Nintendo knows that by now, but there's a LOT of gameplay possibilities in motion detecting full colour cameras. Just Dance on NG Switch? Just put your Joy-Con 2.0 down where its camera can see you and DANCE! Scan QR Codes, use the IR emitter and a second console to transmit user data, or play multiplayer even in airplane mode. Joy-Con 2.0 Marco Polo! One blasts its IR as bright as it can, the other vibrates stronger the more it can detect the other Joy-Con 2.0!
Slap the tablet in a headset and wave your arms around, welcome to the cheapest possible version of premium grade VR!