I think my previous reply to the OP was very confusing.
So try to rewrite it here:
IIn many ways the Sony A7R is not as refined as the D810 is , but it is a lot less risky and also much cheaper to get.
And if you do shoot only landscapes or studio set up work , then there is no difference between the D810 and the A7R.
Thanks for the great reply. I primarily shoot wildlife with a bit of landscapes (would like to do more) and some macro.
For wildlife I will stick, without a single thought of changing, with Canon.
Until the new 16-35 F4 came out, I was very disappointed with Canon WA zoom. The 16-35 F4 is a real winner. If Canon came up with a 5D M4 (or ...) that had significant improvement in DR I would be a happy camper. 36 MP would be nice but also will increase workflow (larger files, more disk space, longer processing times, ...)
The Sony A7R looks like a great alternative and need to try it soon.
Thanks again for the thoughts