It's still a big 'If and when' but once Article 50 gets invoked by the UK, signaling the UK's true departure from the EU, a whole bunch of things will impact the financial markets. Aside from market movements, let's take a look at the possible infra-structure implications and regulatory implications as they have been written and commented by others:
1. The city as the Financial center of Europe
The real effect of the Brexit vote will remain unclear for quite some time. But it is obvious that the City has lost a lot of its attractiveness for financial institutions. Certain institutions will most definitely leave (like the European Banking regulator) and other will take a good look at what their best options are. Whereto then? According to Think Tank Bruegel, financial firms will look at countries most 'friendly' to financials. They take the FTT as a guideline. This would not be favorable for large financial cities like Frankfurt and Paris but cities like Dublin and Amsterdam
2. Regulation and Distribution
Distributing funds is done via the AIFMD passport and under UCITS regulation. Once the UK leaves, the UK companies need to find another way to distribute their business on mainland Europe. Of course there are solutions for this but it will add to their overhead. A good article can be found here.
The uncertainty and the depreciation of the pound will have implications on M&A. Take the LSE/DBAG deal for instance. Aside from the practical matters, the deal has become less interesting for the DBAG shareholders due to the depreciation. True, because of the depreciation one could expect that buying up UK companies becomes more interesting, but experts also expect an 'M&A drought' due to the uncertainty.
The EU always wanted that the clearing of euro denominated products would be done in a Eurozone country. That policy failed but outgoing Financial Services Commissioner Hill expects that the EU will make a renewed push for that ASAP.
Overall, experts agree that the implementation of MIFID will not be stopped by the UK leaving. But will it? What if, as some opportunists have noted, that the City will go rogue and become a 'deregulated city', a haven for companies without all that EU regulatory burden? It would make sense for the EU to counteract and review their own policies yet again.
FINTECH is all about access, access to people and access to distribution. Experts expect that FINTECH will be driven out of the UK because of the Brexit vote and some are already enthusiastically pitching their business. And, remember, the whole Brexit vote was really about immigration and keeping people out. Naturally, this is geared towards the 'lower end' of the immigration work force but this also has an effect on the higher end that FINTECH would love to import.