How much of a threat does the “Brexit” referendum pose for the European Union?

Following the announcement of the so-called “Brexit” referendum on 20 February 2016 journalists and bloggers have discussed the “ins” and “outs” of EU membership, focusing on the arguments for and against, on interpreting the polls, and on reflecting on the success of the Leave and Remain camps during the first weeks of the pre-campaign period. Subject to fewer column inches, however, are the implications of the 23 June 2016 referendum for the EU and the future of European integration. What, then, might those implications be?