The NFL and NHL had better be careful, there are a lot of empty seats in most arenas and stadiums. The NHL has only 2 cities they could move to-Quebec and Seattle. I'm guessing the last thing they want to do is move a team, because they want to find another sucker ( like Las Vegas) to ante up $1 billion entry fee to cover dwindling income. I can see Calgary getting a new arena, but not the 3 in 1 money pit. Doesn't make sense to put all three in one spot. They'd only be able to hold one event at a time because of transit would be unable to handle 2 events at once. And with the Flames owning all four sports teams, they would be tying up the place about a third of the year. 
As far as San Diego goes, most fans wear opponents colours and 8 games that maybe bring 10,000 people into a tourist destination is a drop in the bucket.