I can see the arguments for both sides.
On one hand, the greatest ability is availability, and he does seem to miss 20-30 games every season. He's a free agent at the end of next season, he's almost certainly going to get 8 years from someone and there are valid fears he's not going to age well. And given goaltenders don't generally go for as much as expected on the trade market--even ones who are truly elite like Gibson (if he's interested and you have a good team in front of him)--he might be our best shot at acquiring a true top line forward that the team desperately needs.
On the other hand, when he is there, he's a legitimate shutdown top pairing D about to enter his age-28 season, and even with our track record of defensive development, I would argue we've never come anywhere close to finding someone as good as him in his own end. As much as I liked what I saw from a skating perspective with Fowler in the last game, I think Hampus is the perfect defender with whom to insulate Drysdale, who did seem to get pushed around by bigger top lines as the season wore on. He's immensely valuable to our penalty kill. And as
@Masch78 pointed out earlier, his character and intangibles are impeccable; he's a perfect mentor for the young guys in the room. I'd absolutely hold onto him.