This is just a guess, but I think Harry will receive one, maybe two more power-up's. One will be him learning how to use his Starborn ability. The other I don't know... Perhaps sacrificing his eye for something.
I think another power-up comes when he is summoned to alternative reality and comes back with knowledge or item that should not available in his reality.
This is a post on Reddit, not my own theory. I ran across it and found it very interesting. It basically says that Harry has fulfilled one of the conditions of becoming Mab by giving birth to Bonnie.Sooo....we know from Cold Case that at least the Winter Lady's mantle stops from getting pregnant, because she has to remain a Maiden to be the Lady. If she became a mother, she would be the Queen. We also know that the Queens' mantles can transfer to someone holding the Knight's mantle if another Queen isn't around to grab it. We ALSO know that Mab was mortal once ("I was mortal once."), so the Queen's mantle can transfer to a mortal.