Ok, here come my 2 cents:
CPU: I'd go with AMD's latest bunch of processors, either the 8-core 3800X or the 12-core 3900X. I think that 8 cores/16-threads will be enough, but you may want a bit more. I'd choose them because they're not that far off from Intel's current line and have the advantage of PCIe 4.0.
RAM: Now that prices have fallen down to "normal" levels, 16GB should be your main goal, preferably 3200MHz with the lowest latency possible. That said, if you find a good deal on a 32GB kit...
MOBO: That's the trickiest part. Only AMD's X570 boards support PCIe 4.0 so, if you want to be able to it, they're your only choice. I can only tell you to look at reviews of models you like and see what they say about the chipset cooling. Some boards have a heatpipe that connect it to the CPU's VRMs to help with the cooling, as well as having the fan at idle most of the time (and thus making it less prone to failures).
GPU: If you really want to play at 4K and care about future proofing, there's only one option here: the 2080Ti. That's the only card that can offer 60fps at 4K in almost every game without dialing down the details. But of course it's crazy expensive, so you could go for the second best option, the 2080 SUPER.
Case and PSU: Cases are a very subjective affair, so just pick the one you like the most and that has the features you want. As for PSU, even with a 3900X and a 2080Ti, you're looking at just a bit more than 500W, so a 550 or 600W model should be enough.
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.
