Statistically, he's kind of all over the place, which I think is why you, me, and probably a lot of us can't really tell if he's getting better based on what we see on the field. For example, I've been impressed with his ability to find some deep passes the last couple games, but his running style has also gotten a bit timid and he's fumbled a bunch so it's kind of a big ¯\_(ツ)_/¯.
100% agree you with regarding the future, though, especially if they were to finish with say 7-8 wins or maybe even a bowl victory. It would take a pretty special player to unseat HH even if HH isn't objectively that great of a QB.