It's hard to say what will come in the following years. Slight changes in game requirements, a big shift, a bit of both? It should remain relevant for several years I'd imagine. There will always be some instances of games which are heavily threaded or poorly optimized but those are still the minority even by current gaming standards.
While it's true that some games are becoming more heavily threaded and benefit from a 4c/8t i7 game developers are likely considering making their games available to as many people as possible. The amount of people with 6-8c cpu's isn't exactly a majority of the market, they'd be shutting out people with fx 4xxx, athlon x4's, pentiums, i3's, i5's. That's not typically great for business so the progress toward a majority of games having such high requirements I'd guess to be somewhat slow.
Especially since you're not overly picky (ie don't need 500fps min in cs:go or something) you'll probably remain happy with your i5 for quite some time. The gpu would be worth upgrading but also keep in mind what display resolution you're gaming on.
With 1440p and 4k monitors out there gpu's are working to try and keep up so there are products out there like a gtx 1070/1080/1080ti which may prove to be a bit overkill if you're still at 1080p. It doesn't necessarily mean your cpu is junk if it bottlenecks a gtx 1080 at 1080p, it means at that resolution it's too much gpu. 1080p no longer being king of the hill means you won't need a king of the hill gpu to get good fps with graphics settings maxed out. Getting too strong of a gpu your monitor could be the bottleneck.