It will be on my radar for sure but..... it will have to be a meaningful and beneficial tool.
If Canon take a route map that leads into dead ends of crippled functionality or decide ghat they want a fast return on their investment, then who knows?
The simple fact is that the ‘Pro’ users will have their business hats on and that means the equation between investment balanced against cost/benefit and cost of ownership - (use of current peripherals).
The serious amateur and part time semi pro have similar needs but, again, price and cost of ownership are a basic.
For me, the M series weight balanced out the restrictions of my changed and changing health limitations. I can no longer cram a 400 backpack with a heavyweight D kit along with a tent etc and disappear for a couple of days. If the FF does not compromise my limitations ghen yes I will be looking at it.
Steve
I'm with you on the health side, I ditched FX gear years back because after back surgery it was a chore, a pain, literally, to cart around 10KG of gear just to take some simple photos for pleasure. I had decent money at one point, and I thought buying a tonne of FF gear would please me no end, and it did for a while, but then it felt cumbersome and weirdly restricting. I'd look at all this gear and think 'F me, I only want to go down the river and take a few shots'

I was doing the odd paid gig too, which did help pay for a lot of it, did some weddings, christenings, parties, family portraits and music gigs and enjoyed all of it. But that got too much too, some forget how physical these gigs can be, especially if you have any ailments.
So no, I never want to go back to bulky FF gear, if I did happen to get a FF body I would be looking to light primes mostly, there really isn't that big a difference if you go that route. Mirrorless is making this much more possible, not because the bodies are smaller and lighter - which they are, but because the overall package is much lighter in general. Every kg counts!
Unlike many on here who can eye these things up and simply decide on specs, budget is a huge factor for me also. If not, I'd probably already own a Sony A7III and some snazzy Zeiss primes. The rumors suggest that Canon are aiming for the mid-range, and it will be a fair amount cheaper than the Sony or Nikon offerings. And it will be a lot more budget friendly if it turns out to be the case that the mount is backward compatible. I have no problem paying up for a reasonably priced good camera and just grabbing a 50mm or some adapted glass until I can save up for better. I've done it before. I also have no problem selling off the kit I have to make it happen.