It's unlikely to make any difference whatsoever. Just like all the other threats being made around the Brexit.
Now in advance of the following comment, I am an undecided voter on the subject.
Just like all of the Brits based in Spain in bars etc that generate huge incomes for Spain, do you really think the Spanish are daft enough to cut off a revenue stream by booting out the Brits? The reason schools like FTE and us recruit Brits and other non Spanish is there are no Spanish candidates. Would the Spanish government run the risk of shutting down tax paying companies that employ Spanish staff in other capacities by booting out the key staff? Me thinks not.