Update: See the video on this page for a viewpoint on why mirrorless is so important.
So, it appears that next year, Nikon and Canon will finally get their act together and make a professional mirrorless system each.
I think they definitely will need to make a new lens mount and lenses, because keeping that huge old distance from lens to film is ridiculous. (The mirror necessitated that.) With a good adapter, people can use their old lenses for a while.
But, and this is important: I also think that for many of us, Full Frame is a dying system. It’s just too large and heavy, and unnecessarily so.
Already now, sensors are so good that the half-sized (linear) Micro Four Thirds sytem has plenty good enough image quality for professional use, and the cameras and lenses are the perfect size. (Small ones for casual use and hand-sized ones for professional.) And only half the weight of full frame gear.
And sensors are still getting better every year. In ten years, FF will be a dinosaur. Zat iz mi belif.
With the fastest lenses, you can get good background blur with M4/3 too, although of course not as extreme as with FF. But interestingly, with digital tools as in iPhone X, this can even be done in a phone. OK it’s not perfected yet, but I expect it will become so. And when it works well, it works surprisingly well!
“Canon has noticed the explosion of interest and progress in mirrorless cameras, and it’s trying to join the party before it’s too late. Nikkei reports that SLR sales dropped over 10% in Japan in 2017 while mirrorless sales rose nearly 30%.”
Canon and Nikon has a huge amount of catching up to do now. They have simply been way too afraid of canibalizing their ancient (D)SLR lines. Fear keeps most companies from realising that if they don’t eat their babies, other animals will. That Apple is not afraid of this has helped make them the most profitable company in the world.
Not that I don’t think CaNikon won’t win back their share. The world is not often “fair” that way, it’s rarely the innovators who take the big harvest.