No they won’t. As soon as they are aware the price fluctuates they’ll go somewhere else. Wendy’s competitors will be watching this to see how many more customers they receive during Wendy’s “surge pricing” hours.
Uber “gets away with it” by saying they have a limited number of drivers, and you can always see the price on your phone. Nobody is going to go to a Wendy’s if they don’t know what the prices are going to be.