That ticket has not been updated in about 6 months....
I hope they do support it. Edge as well. The more browsers/OSes that do the more demand there will be for Chrome to support it.
Edge et al are not going to support it unless Blink does. Firefox and Apple will have to lead the way here if Google doesn't.
MS can extend Edge (and its version of Blink) with whatever support they want. I could see them supporting it to hinder Chrome/Google honestly.
Good point (embrace, extend, extinguish), but if they try I doubt they could compete with Google on Blink development here.
It isn't competing with Google on Blink development, it's simply adding support for the new JPEG image standard (which they're probably going to have as a system codec anyway in that case). Note that they've had HEVC playback support in Edge before Chrome.
They could just maintain it as a patch, so the development cost would not be too high.