I really want to see what would happen to that theory after a Brexit. Would the economical/financial benefits of a closed border policy outweighs the economical

I really want to see what would happen to that theory after a Brexit. Would the economical/financial benefits of a closed border policy outweighs the economical/financial benefits of being a member of the European Union ? If so then that's really bad for Europe image, if not then that's really bad for those financial super powers to realize their judgments are really biased. The third option being: the analysts here really messed up and shouldn't make a connection between a stance on open border policy and an outflow as consequence.