Difficult to say how it will affect sales of watches (or indeed any goods) in the short terms at least as it's a period of great uncertainty for everyone this side of the Atlantic, although I think it's fair to say that prices in the UK at least certainly aren't going to drop!
On a more personal watch-related note, leaving the EU is a pain in the backside for me as over the last few years I've bought and sold a number of watches throughout Europe taking advantage of the zero tax and import duties. Italy for example has been a great source of very well-priced watches, in many cases only very slightly more expensive than they are in the US but without the import and taxation implications I get with US/UK trade. So it's goodbye to that.
Once we're no longer EU members I fully expect to see a minimum of 20% added to anything I buy from Europe just due to VAT alone, and then there will be import duties as well, before we even start to get to standard P&P. Great.
