Quite right. No one has yet confirmed that he can be a top-pairing D. Guhle has that potential, and arguably Reinbacher and Hutson do, too, but it'll take some time before we know whether any of them can play at that level. Others (such as Engstrom, Mailloux, Barron and Xhekaj) are more likely to have second-pairing ceilings, but they aren't proven yet, either.
Overall, I am very optimistic about our D prospects but they are still very, very young on the typical D development timescale.