"What will happen when the Swiss referendum bombs?"
I have been looking through the local German and French language commentary, and I can't find anyone who seriously thinks it will pass. The last poll was 39-47.
My impression is that traders have been using the recent rally to square up. (The COMEX open interest is down over 20% in last two weeks.) I doubt very much that there are material long positions held in specific expectation of a "yes" vote. So there shouldn't be a run for cover on the down side.