According to recently tests by Photonstophotos, Sony Alpha a7RII has the better dynamic range than new announced Nikon D850. Nikon D850 also uses BSI-sensor as a7RII, it seems Nikon’s BSI technology isn’t as good as Sony’s.
Sony a7RII is already two years old now, and the replacement a7RIII is rumored for a long time, according to previous rumors, a7RIII will be announced in 2018, stay tuned for more info.
via: Photonstophotos