Look for the exodus of business from Seattle. Also look for the consumers to migrate to the businesses outside the city as the prices will be lower outside the city.

The only things this accomplishes is to discourage productive and creative workers, and raise the cost of goods and services.

If any lazy waste of skin can collect $15/hr, the company will be that much harder pressed to pay the productive, creative workers merit pay above that. Companies need to have unskilled labor, bodies to do menial jobs (jobs that will oneday be done by robots... wait, they are now... make that "mechanical robots"...), but the more you pay the guy off the street to do those menial jobs, the less room you're going to have to pay the quality workers what they're worth relative to unskilled laborers.