If it's clear that you have good reason to close the store, then you close the store. If you're closing a profitable store to avoid unionization, then you don't close the store. There's no need to wait, just don't close profitable stores in retaliation for union activity.

It's just like now: if an employee is bad, then you document it and fire them. If you're firing them to avoid unionization, then don't fire them. There's no need to wait, just don't fire employees in retaliation for union activity.