Seattle are a totally different story, they can sustain an NBA team, the reason they were moved to OKC isn't due to money but local bragging rights, the then new ownership group of the Supersonics were all OKC born and pledged to bring a team in their home town. As if stands Seattle will get an expansion team in the near future, as will Las Vegas and Tampa or a team is going to move in one of these cities, for example if the Timberwolves moves, Minneapolis-Saint Paul will get an other expansion team down the line.
In the case fo Seattle they are getting the NHL team this summer and will be a four major sport city before 2030.