There is an issue on SDK staking: bump all commission rate below param · Issue #10540 · cosmos/cosmos-sdk · GitHub and also a PR feat(x/staking): update validators min commission rate after `MsgUpdateParams` by julienrbrt · Pull Request #19537 · cosmos/cosmos-sdk · GitHub. This means that once we update to this version of SDK (probably 0.51), upgrading the MinCommissionRate param will automatically bump the commission rate for all validators.
@Flo thanks for bringing this up by the way 
It’s a very good point.