[jacquesm]

I think that one major reason this did not happen so far is because the rest of the EU was hoping the UK would come to their senses and cancel their brexit ambition. Now that it is a fait accompli you can expect all these things to actually happen. Frankfurt has good chances, Amsterdam and Paris a bit less so, Switzerland does not have any better position than London so I fail to see why that would happen if there would be a reason to move. Whoever wants to be represented in Zurich is already there.