The i7 is not where we upgrade for better gaming performance. For gaming we look to the GPU. As to 3 years, the outlook is still to the GPU for how to improve the gaming at the usual 1080 to 1440p gaming.
I currently have an asus z270 tuf mark 2 motherboard with an intel i7- 7700k and i mainly use my pc for gaming. I dont want to upgrade to a newer processor right now but i was curious if their would be any real benefits to upgrading to another z270 motherboard. Specifically the rog strix z270e or the asus Maximus ix code. If i plan on keeping my pc for another 3 years or so, would it be good for me to upgrade or just wait till i build a new one.