- Like what you've got: stick with it. Yes, the D850 has moved the bar forward again, but those older models still produce great images.
- Dislike what you've got: consider the D850. That's really your only DSLR choice for D800/D810 users. The D6 is a downgrade on the pixel side (though it does up the fps and body quality). A D610 or D780 is a downgrade in pixel count and in body quality in the case of the D610. Frankly, if you're in this category and are looking at the downgrades, you went too far with your "gotta have the latest" buying, and you need to take a good strong look at that problem before figuring out what to do next.
The question is whether D800/D800E owners should upgrade to a D810 or D850: if you’re filthy rich, sure, why not? The D810 fixes a few things and add some nice touches here and there over the D800/D800E. It feels like a different camera despite the fact that many of the changes were small. The D850 does that in spades over the D810. From a pragmatic sense, there’s not enough there to justify the cost of switching up a model at the moment, though a D800/D800E owner should strongly consider moving to the D850.
Should the D810 owner switch to the D850? Much tougher question. If you have the money, you will find that the D850 advanced the bar considerably in most areas—though it loses the built-in flash—and is arguably the best all-around camera you can purchase as I write this.
The Z7 II looks interesting to the D800/D810 user, but this is future (Z7 II, mirrorless) versus establishment (D850, DSLR). Are you really ready to move to the future?
