The demise of optical viewfinder cameras was to be seen about 10 years ago. Thom Hogan in his blog was one of the first to note and elaborate about the lack of understanding the established camera brands had to new challenges, especially for the role of software and a workflow.
Meaning: Most of the mainstream companies had really lost the contact to the customer and the way stuff has to be handled, and instead of listening to the trends, they continued to produce cameras with a technical better image quality, but otherwise no changes.
In the meantime, the lower end market acutally has been assimilated by smartphones, the whole area where workflow really matters still is not understood well by nearly all traditional camera manufacturers.
As a Nikon shooter for a long time, I still have some analog equipment with me, and what is nice that Nikon managed to be able to use lots of the old lenses from as far back as 1977 on modern DSLR, which can be benefical with some special setups. But, the writing was on the wall for a long time, and now Nikon as one of the last established companies has successfully turned to mirrorless with their Z-Series, and finally made lots of things right, after some "dipping the toe half-heartedly into the water" with the Nikon 1 Series failed miserably.
Actually, with the recent introduction of the Z30, Nikon has a full portfolio of cameras at their hands, from entry-level to pro body, and the lens setup (Note: Nikon always was an optical company, not necessarily a camera menufacturer) is something that begins to be useable for most needs. Still something in the DX/crop sensor setup that is desireable, but beginning to be reasonable.
Regarding optical viewfinders: They have still some value over mirrorless cameras in special situations, but as mirrorless is getting better at this stuff, it actually is more than useable in everydays shooting. For sports and wildlife photographers an optical viewfinder still has no lag, and in case of flash photography (fill flash etc.) there are moments where a mirrorless camera still does not displays the environment right. Also the battery life is better, which matters especially in nature photography when you have to pack light.