I will probably add one mirrorless to my bag, but since digital cameras are essentially computers I will patiently wait maybe a couple of years so they can fix the bugs and release the "S" version like they did with D3S and D4S. I never bought D3 or D4 but the "facelift" instead and both have been problem free and perfect from the day one.
I have shot a few days with a Sony A7R III and there are a few things I don't like. First, the EVF is still very far from perfect, currently I'd give it a high school grade of D. I have shot 40+ years with both eyes open so my left eye sees the scene and my right eye is on the optical viewfinder. This way I know what will next enter in the frame. With an EVF this is not possible really, in the evening/night the EVF is too bright and in daylight it is too dim. For two-eyed shooters current EVFs are a no go.
Secondly, there's the delay. For a two-eyed shooter in those rare circumstances that both eyes can be kept open, the video feed in the EVF is out of sync with reality. It is a little behind... the delay is not long but it is there. It is disconcerting watching the same thing happen twice... first with the left eye and right after that with the right eye.
Third, while the EVF frame rates have climbed up and Sony now offers 120 fps it still isn't "analogue", meaning infinite fps. Maybe in the future something like 500 fps EVF will start to feel like looking at the reality, not like looking at a tv.
Fourth, Using the electronic shutter curtain there's no noticeable viewfinder blackout... well this is a two edged sword. I need some confirmation of the actual moment the shot was taken, and with no blackout and no shutter sound I have no idea if and when the image was captured. Some kind of "click" sound would be necessary, or I'd prefer a blackout of the evf at least in single image mode. With bursts the the situation is different.
Anyway, as I said I'll add one mirrorless Nikon FF camera into my bag a little later when the "mk II" or "S" comes out, and I'll use it for things that it can do better than a DSLR, like using f/0.95 lenses and when soundless operation is necessary. And I'll only use it with native Z-mount lenses, adapters are definitely a no go.