CitiFX has crunched some numbers to lay out the Brexit scenarios for the GBPUSD and EURUSD
"Whatever the outcome of the referendum, trading should expect contagion (both good and bad) is not limited to the UK. The macro outlook for Europe and 2017 political risks in Germany, France and the Netherlands are all tied to the UK’s decision. The most immediate wind-test for Europe should be the Spanish elections set for Sunday June 26th (which by themselves create EUR risk as well).