I'd be happy either way - but I do really hope they give it an M-mount. Either way you look at it, there isn't a ton of affordable APS-C glass for either mount, but I feel like the M has the better chance to have that library extended. We DO already have amazing 22mm and 32mm primes, a couple more primes and a couple more solid zooms for that mount make more sense to me than building an APS-C lineup from the ground up, or forcing people to buy expensive full frame lenses when they won't be used as such for at least a couple years until they MAYBE upgrade to a FF option.
Frankly, all I need in an updated M camera would be an M6ii with a viewfinder, IBIS, and the 10-bit C-Log from the R6, which I think is very reasonable to ask for. There's plenty of things I think they could add to sweeten the deal, but that would make me plenty happy.
The appeal to the M series to me is its versatility. I can throw my 22mm on and have a jacket-pocketable point and shoot, or I can adapt my EF-S stuff to it and get some really solid professional work done. If I had full frame glass, they even make speedboosters I could use with it. So I'd love to hold onto the M system to keep that versatility. Throw in a battery grip and MOVE THE HDMI PORT OFF THE GRIP and I'd be over the moon.