I would agree with Ilkka
Many photographer today "have" to deal with video (though it's a completely different media), for corporate or marriage and maybe even travel or events, mostly because of web access and presence for corporations' sites or blogs.
Others can still operate with still photography as "Art", wildlife, macro, fashion, even reportage, etc. because it's either printed in magazines or in photo books or again in galleries.
Mirrorless is an easy access to video (Z6) with the capacity of having great stills (Z7, Z6), for marriages and corporate, it's a light weight, multi purpose tool (even with the needed additions), but for wildlife, portraits, landscape and even street, the OVF is still for many an asset.
I don't think the SLR are dead or dying, as we do see the resurgence of film when many said it was dead and buried. Even youngsters who are already quite good with an iPhone try to learn film processing and buy (cheap) film cameras, not all of those jump to mirrorless and video !
The good news is that now we can have several tools and can choose the one we need (or can afford)