Not that they have formally left yet, but I think a majority of them know that it was not their finest move. Indeed, the vote to leave was not exactly won by an overwhelming majority.
But Merkel can't make this work on her own. The twin dangers of crushing bureaucracy and toleration of government corruption at both the federal and the local level are still dire dangers that the EU has been reluctant to face head on. There are some police forces that are really nothing more than professional theft rings.
The huge proportion of "Beamten (fonctionaires en français)" hinders life in Germany at every turn. These people are there for life and enjoy privileges that are unheard-of in the private sector. They can never be fired, and the indifference of many of them to the public shows it. Until public workers are required to display the same degree of responsibility for their actions as employees in the private sector, progress will drag unnecessarily in the EU. As in the USA, resistance to reform and progress is powerful and well-established.
PCF boss Georges Marchais was once asked if, after getting elected to power, if they would give up that power if the people were to vote them out office in the next election. His answer was, "why would anyone ever vote us out of power?" It's logical that an avowed Stalinist would give a Stalinist answer, but his attitude was not a notable exception.