- Like what you've got: Of course you do, stick with it.
- Dislike what you've got: Stick with it. Not exactly sure what you dislike. The only realistic side-grade path is the D850, which means you bought the wrong camera in the first place. Your other choices are the D5 or D6, or to switch to a Canon 1DX Mark III. You'll be giving up body build, vertical grip, battery endurance, and more in order to gain resolution if you go the Nikon D850 route. Jumping to the D5 or D6 really is mostly about the autofocus system. I generally don’t recommend upgrading every generation, and would suggest that you pick the D6 if you do decide to upgrade. The one thing that you should consider is that Nikon will likely move to mirrorless in this line in the future (e.g. 2021-2024).