Wrote a long post about Hanifin and lost it.
Not sure about expansion slots, so it may be a trade best explored after expansion or with expansion in mind.
He skates well--he's big at 6'3," and while he's 215 pounds, he still has space to add muscle. He's been playing 21 minutes per night with Calgary (up from ~18 with Carolina). His defense took a hit with Calgary, but his partner has predominantly been Hamonic (who is significantly worse without Hanifin). Paired with someone like Trouba his defense may rebound.
I hope I'm wrong, but I can't see Miller, Roberston, or Jones ready to jump into first-pairing minutes. Even with Hanifin in the fold, not the worst problem.
Hanifin - Trouba
Lindgren - Fox
Miller - DeAngelo
That's a young defense with a lot of room for improvement. Hanifin's contract is about 5.8% of the cap. Staal's was about 8% at the time of signing, so it's lower when adjusted for cap percentage.
Everyone was talking about Edmundson, but Hanifin is younger, and I think he has greater upside.
$4.9 million would be pretty movable.