CPU now, GPU soon*. I had a 2500K OCed to 4.7 GHz and upgraded it last year. Then I upgraded my GTX 970 a couple months later after the Super cards were released. I wouldn't do it any differently.
Your 2500K will bottleneck any new video card you pair it with. There's no point in spending $500...
I foresee a ~40-50% performance gain when utilizing RT and DLSS over the 20x0 non-Super cards as they'll be better tailored for those now more mature technologies. But without these features enabled the gain in overall performance will only be another ~30-35% for each card tier.
I also predict...
"Whataboutism"? Whataboutism!
It's ok if you can't think of a response beyond that. I know it can be difficult for some people to be introspective and think critically.