Touch ID, maybe. Multiple accounts, most likely no.
If the pixel density of Air I increases, then the mini also has to increase, because Apple will want to keep both devices at the same screen resolution.
32GB as the base storage option would be wonderful, and must happen sometime, but whether that will be next year, I'm not sure.
Color of the back, I don't care about, because I always put on a case. As long as the front is black, I'm happy.
The rest I agree do sound likely.