I don't get why anyone would be interested in this camera at the moment. It's probably a solid camera, yes. But it has a bad 4k crop, no 120 in 1080, generally not the best video functions. And the resolution isn't better than on other models. It isn't cheaper. It's a bit lighter, yes. But with the newheavy lenses it doesn't matter anymore. I don't see any reason, why I would buy this body at the moment, and go mirrorless. I'll wait if they come around with a more pro like body, that really offers something new, that gives me a reason to buy a new camera, because it does something, that other body's can't do.
I do not know why you would buy it either. It will not fit all your Sony / Nikon lenses.