Here is a straight forward answer for you cause I see no others,
You are not being bottlenecked by the I5, you could even get a more powerful gpu and still be fine, I used a 3rd gen I5 with a GTX 1070 and it worked fine, in some games my I5 bottlenecked it, but in most it worked great!!
As long as you don't have any problems with playing games you want to, no need to upgrade, I still run 3rd gen intel cpus because they still work great, but you know, that's just my opinion