Fstoppers explains why Canon isn’t happy with the Sony A7III release:
If they release a mirrorless camera that’s too good then they risk cannibalizing their current line-up. Although Canon has discussed how they are willing to cannibalize their current line-up this sounds more like lip service. Unless Canon has set aside a large enough cash cushion or they release a fully developed line of cameras, lenses and, accessories in a very short period of time, they won’t want to undermine their current systems. Chances are, Canon was probably going to release something relatively mediocre based on current standards. Unfortunately, if they do, many Canon shooters may feel that Sony is the better option and this is primarily down to the fact that the a7 III is such an incredible and cost-effective option. As mentioned above, the cost of entry for Canon is much greater now because of this intentional and strategic move from Sony.
Just my two cent: Canon’s goal is to keep their own DSLR folks on board offering them a Mirrorless alternative that works well with current EF lenses (via adapter). I don’t think the A7III did ruin their plan. Canon hardcores will porbably keep using Canon.
Some more A7III news:
Maarten Heilbron review of the camera:
And a new video from David Oestler: