Looks like nice growth to me! Cephs are very slow growers. And no predicting adult pitchers. It just happens. I'm growing a few from seed and it's looking like I may not have them flower for 3-4 years.
It might do with more light, but Cephalotus will grow in relatively shady conditions too (you might find more leaves than pitcher however). The transition from young to mature pitchers is not a gradual thing, it will happen between one leaf and the next, so as mentioned predicting when that occurs is simply a roll of the dice.