I have the XT2 and I think is a very good camera; don't know the XT3 but reading some of that it's written about this camera and a bit a knowledge over the standards of practice of the camera market I don't think this new camera go provide very big improvements over the XT2, of course, it depends very much on the personals tastes and types of photography you do. But, in my humble opinion, one thing is crystal clear and is the very, very superb quality of the lens in question, the XF 56, that is arguably one of the best lenses of Fuji and probably of the photographic gear in his class.
P.S. Sorry for my horrible language.
Thank for your time