I don't think this is their high-end full-frame mirrorless... It's just $2299, which is nothing like the price of a 1DXmkII, despite this requiring a significant engineering investment for the new mount, body, and glass. I think this is a declaration of intent more than anything.

As someone mentioned in the news comments, we now have two incompatible EOS Mirrorless lenses standards, M, and RF. I'm curious if the M mount will be positioned like an EF-S, and M will remain as a cheaper crop-mirrorless option, and future crop bodies will be able to take RF or M lenses. If you see yourself upgrading to a full-frame in the future, you can pre-invest in the RF lenses for you M body. If they remain completely separate, it would suck.