^ The only thing in that list that would really need 15,000 seats in the sense that the events probably wouldn't happen without the seats is the World Juniors. Every other event could use the seats on occasion, but would probably happen either way... the NLL for instance has several teams in 11,000-ish capacity buildings.
Realistically the Blades don't need more than 6,000 seats tops. I actually find it a bit strange that the Blades are not better supported considering their lengthy history.