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I don't think you need to worry about whether Canon will persevere with the EF-M mount, I believe it's a foregone conclusion they will.
It's "small", flexible in many of the same ways the EF mount is, and represents a new market for them.
If there's any mount/system I think Canon would dump, it would be EF-S. The lenses are really not that different in size or price from many of their EF counterparts, so the benefit/drawback comparison doesn't really work out much for the benefit side, in my opinion. Sure, you have some ultra-wides that the EF lineup can't approximate for APS-C, but all things being equal I am hard-pressed to think of other notable pluses.
EF-M is here to stay, I say.