"Evolution is change in the heritable traits of biological populations over successive generations." Because of DNA's propensity for mutation, every procreating DNA-based species is by definition undergoing evolution. Thus, humans are evolving.
The term "humans" is misleading. "Humans" can mean the set of living subjects of the homo species, each of which is not evolving. If a predicate is false for each unit in a set, then it's false for the whole set a well. "Humanity is still evolving" is more accurate sentence.
it is well established in the medical sciences that there is genetic diversity between different lineages of humans which must be taken into account when designing treatments. Humans are still exposed to the same selective reproductive pressures which resulted in the current genetic differences.
The concept of evolution says we must be evolving. However, if something was to somehow stop us from evolving, then we would not be able to know this. Evolution is too slow for us to verify that it is still happening.