It will be interesting to find, as time goes on, what will setup just across the city boundary. It is a well known phenomena in the Northeast for liquor stores, cigarette shops to be on the ‘right’ side of such imaginary lines.
As for fast food within Seattle, automation will come. Make a labor cost significantly higher and entrepreneurs with thin profit margins will look for alternatives!
Those running my city raised the sales tax two times, each time by .5%. So the sales tax in my city is a full 1% higher than surrounding cities. I, and many I know who opposed the increase drive a mile or two extra to make major purchases. It adds up.