Seattle? They couldnt support a NBA team.
That's not entirely true. They supported their team really well for a number of years up until that very last season when it was announced they were going to move. What it boiled down to, as they all do, was they couldn't secure a new arena. The team was sold to a businessman in Oklahoma City who swore he would try to secure a new stadium. Instead, he let them play one more year in Seattle before uprooting them to OKC.
That said, I'm not sure how they'd do with a hockey team. The NBA almost came back there this year, but the Kings stayed in Sacramento. I would think if the hockey team was the only winter team in town, they'd draw a crowd. But if the Sonics ever came back, I think the hockey team would be left in the dust. Pure speculation on my part, obviously, but Seattle did support the Sonics, and they have some of the best fans in the NFL (Seahawks) and the MLS (Sounders). They know how to support a team.
I feel bad that KC built that great arena and yet they can't draw an NBA or an NHL team. I do believe they would support a hockey team well. They've been starved to get a 3rd major sport in there for awhile, it seems.