Basically… yes, according to Morgan Stanley, who have however outlined one tortuous alternative path:
We do see a political route to reversing the decision – a new parliament with a majority for a pro-Remain party which is either elected on a reversal platform or subsequently holds and wins a new referendum on reversing the decision. But this is quite an ask:
First, the reversal of the decision probably has to be done before the UK actually exits, since at that point the UK may lose its special status (its opt-outs from the euro and Schengen and the rebate), which would significantly reduce the attractiveness of EU membership. This, in turn, would require early dissolution of parliament. That would requires some Conservative MPs to vote against the government, given that the condition for early dissolution is: a) A two-thirds majority of MPs voting in favour of a new election, or b) That the government loses a vote of confidence(and that another government cannot be formed within two weeks). Second, there is a risk that if the EU and UK get into an acrimonious divorce, then UK political sentiment will harden behind Leave.
As we went to pixel, David Cameron was telling the nation that he would step down by October (when the Conservative party’s conference will be held). He will leave it to Britain’s next prime minister to notify the European Council of the two-year withdrawal period provided for under Article 50. The UK is delaying already.
And that’s assuming the next prime minister avoids an election in the meantime as Britain’s politics goes through its most extraordinary period since the end of the war…
More in the usual place.