If they segment eras of cards, Column, as MTG does then although you might be seeing a raising of the card power right now with Naxx, it will plateau at whatever level they decide to set it at, whenever they start to phase out old cards. It will be like sea-floor spreading and zones of subduction. But if they never retire any old cards then yes, Warlock will most likely get better eventually. Although even then, the rate at which it does so will decelerate over time. Either way, Warlock hero power is borderline broken.
So shut up, you aren't necessarily right or wrong and neither is he. It has yet to be seen.