The ceiling of any player is the optimistic outlook... The floor the pessimistic one.
Question is wether a prescribed ceiling or floor is an accurate / realistic assessment.
I think Barron's ceiling is a top pairing regular. His floor (barring career altering injury) a 6-7 dman & NHL regular.
It would be optimistic to assume or take for granted to reach his ceiling, but I don't think top pairing D is an unrealistic or unreasonable ceiling based on what he's shown this far as a 22yrar old, 3rd year pro.