Even an i5-6500 will be more than enough for most people and most games for the next 5+ years.
At the 6-7%/year rate CPUs have been improving for the past several years, you can expect CPUs from 2020 to be only ~35% faster than current ones. For most people and uses, this is won't be worth bothering with.
Until more applications and games make more effective and efficient use of multi-threading, even an i5-2500 will remain relatively future-proof.