As reported earlier, Canon's next full frame mirrorless camera will most probably have a brand new sensor, perhaps in the mid 20 to 30 MP range.
Nikon is also planning to announce their full frame mirrorless camera, perhaps some time in mid 2018. Canon is expected to be cautious again and let Nikon take the lead in the new camera introduction. The earliest Canon may announce their full frame mirrorless camera is probably late August 2018, just before the Photokina Show in Germany.
Canon is a huge conglomerate and the biggest photography equipment manufacturer in the world. They have multiple full frame mirrorless projects in their labs. However, unless Canon decides to bring out their full frame mirrorless body with the EF mount, they will still be playing catch up to Sony's formidable line of full frame mirrorless cameras. The successor to the highly acclaimed Alpha A9 will be on the market by then.
The only way Canon can differentiate itself from the pack is to announce a top-of-the-line, full frame mirrorless camera that will interest professional sports and wildlife photographers, and the ace in Canon's pocket is a mirrorless camera with the EF mount, enabling photographers to use the vast array of EF lenses on the market without any cumbersome adapter.