Depends very much on what you want to play. Esports titles, probably a very long while, but the cutting edge games are going to be a challenge in a year or two most likely. These may not be games you want to play though. Star Citizen is certainly a game ahead of the current mid-range gaming platforms, but they are still in the early stages.
I know you said not to, but if you can locate an i3-8100 and Z370 board, that should be cheaper than an i5-7500 and be just as fast, and give you a moderate upgrade path. Same with the Ryzen platform, the higher core count there would be better suited to newer titles. Using something like BF1 as an example CPU threads are very important for high FPS, and that trend will likely continue.
I wouldn't worry too much about the GPU though, if you are targeting the mid-range now, then you should be on a relatively quick upgrade cycle and be able to pick up a new GPU in 2-3 years. Selling your GTX 1060 6GB for whatever you can get at that time should make it a relatively cheap upgrade.