Unfortunately his upside short and long term are low in this situation.
Barring an injury ahead of him, I doubt he sees significant snaps this year. Car will be in a lot of 2 and even 3 TE sets (Williams/Tolbert playing halfback) and sometimes Benjamin will be the only WR on the field. In passing situations the veterans Cotchery, Avant, and a dependable Bersin seem more likely to be on the field than King. I think there is still a chance King doesn't make the 53.
Bersin hasn't proven anything, let alone he's "dependable." King has a lot of upside, and one of the reasons Carolina didn't draft more WRs was the presence of guys like King on the roster that Proehl felt could continue to develop.
I agree Benjamin is the one and will be on the field in 2 TE sets, but Carolina didn't run them that often last year, and may or may not run them very often this year. A lot of teams say they want to run a certain personnel grouping, but often find themselves putting the best players on the field.
Benjamin, Cotchery, and Avant are locked in, but there's no promises past that. King could very easily claim a spot and continue to climb. Avant isn't much standing in the way.