I have been reporting for some time now Canon's plans to finally get serious about their mirrorless camera line. It is no secret that Sony is ahead of Canon in this field but may not be for too much longer. Even Leica has introduced a full frame mirrorless camera last year, ahead of Canon.
My sources told me Canon will announce the EOS-M4 camera first and then the higher end, full frame mirrorless camera with 4K video some time in the second half of 2016, perhaps around the big Photokina Show in Cologne, Germany in August. This should not be a surprise to most people since Canon has been quite 'vocal' about their ambition since last year.