Well, my 2017 shopping list just got a lot more interesting!

Great that we have a range of different systems to choose from now, each with strengths and weaknesses. I'm interested in the Fuji, but the draw of Hasselblad colours and leaf shutters is considerable.
The longer I use the A7RII, the less bothered I am about EVF vs optical... and the lack of a bloody great mirror going clunk before every exposure certainly helps hand-holding.
Really, we are absolutely spoiled. There's hardly such a thing as a bad camera on the market. I can see selling points just for my own photography for the 5D Mark IV, the 1DX2, the GH5, the H6D, the X1D, the Pentax 645Z, the GFX, the OM-D E-M1 II, and I'm sure the smaller-frame Fujis have their appeal too (as do Nikons and whatever Sony will come up with after the A7RII of course).
Actually my main hope is for a bit of convergence, so I can rationalise my lens collection. I've got the equivalent of 28 mm, 35 mm, 50 mm, 85 mm, 105 mm, 70-200 mm zoom and standard zoom in four different lens mounts already, not counting the case of "junk" glass M42 thread lenses I use on my RED when I want a softer film look, and a whole case of more exotic speciality glass like 180 mm macros and the like which I'm sticking to EF mount for, for the forseeable future (they're usable on the RED, and the A7RII with Metabones).
... and that's probably the number one flaw in the GFX for me as announced- yet another lens mount to collect. A lot will depend on the price when they finally arrive. If they are circa the same as the Hasselblad lenses, I'll probably just stick with Hasselblad.
Cheers, Hywel