I mainly shoot with 2 D5, but own a D500 and have shot with a D810. For travel and landscapes, I'd definitely go with the D810 14-24 & 70-200 combo. The detail with the D810 is just incredible. The DR at low ISO is really good (check out DxO). With the D500/16-80, you're starting at a 24mm equivalent, if that matters to you. The 14-24 is really wide on a FX body, maybe so that you might want to go with a 24-70 to compliment it, but landscapes over 70mm can be really nice too.
I haven't had great results with Auto AF Fine Tune - I use my regular LenSpyder for all of my bodies and lenses. I think the D500 has the lit up buttons too, but I've never used it on my D5. Between what you see in the viewfinder and what you can get with the info button, it's all pretty well covered. If you're doing landscapes at dawn or dusk and you really need to see something else, a little pen light will work.
I think the strong aspects of the D500 are for when you need the extra reach of a DX body or if you need a better AF system for sports or wildlife, or the 10 fps. Otherwise, I'd go D810 or even D750.
I don't like guessing about yet to be announced cameras or bodies, but I did get rid of my 70-200/2.8G when Nikonrumors had enough posts about the new E version coming out. In hindsight, I lost money by frequently renting a 70-200 than I would've taken a hit on selling a 70-200/2.8G after the E version came out.