I have a Canon M5, as well as a Canon 80D (and a number of older DSLRs, etc). While I generally prefer the 80D (for a number of factors including ergonomics, battery life, lens compatibility, etc).
However, I bought the M5 for 3 specific reasons:
1) Samyang / Rokinon 12mm f/2 (a great lens for astro photography)
2) When I need / want to take along a smaller camera / lens combo
3) I bought it 2nd hand, but in as new condition, for a very low price (along with 15-45mm, 18-55mm, and 18-150mm lenses).
If Canon update the M5 with certain goodies that will be of value to me, I will probably sell my M5 (with 18-55mm) and upgrade to the M5 II. I would make some $ selling the M5 on the current 2nd hand market.
Most important aspects to me would be good sensor / IQ, at least as good ergonomics and potentially better AF (e.g. low light, etc).
PJ