Expectations are things that we think will happen. Also, we expect them. Sober, in some connotations, means not drunk. Also serious. In this case, it means serious. However, I do not think the founding fathers were generally drunk
Having said that, a revolution of sober expectations, to me, means a revolution that was not based on revolutionary ideals, like many other revolutions. Rather, it came about as a process. The American Revolution officially started in 1776. However, it did not just happen. It came about as a result of scores of years of history. The colonists had governed themselves without much British interference for a long time. When the British started interfering in colonial government, the colonists wanted representation. When they did not get it, they were angry because it violated what they viewed as their natural rights. The revolution was based on ideals that had been around for a long time. There had and would be many other revolutions. The difference between these and the American revolution was the fact that the American revolution was a slow process, eventually culminating in the colonists fighting for independence. The colonists were not trying to build a utopian society. They did not think they were going to form the perfect form of government, or make some amazing society. Their expectations were not unrealistic, or even terribly high. They wanted to be represented, and they wanted to have a government that took into consideration their needs. At the time of the American Revolution, the British Parliament was no such government, with their ridiculous idea of virtual representation. The phrase “sober expectations” means that the people did not think that they were going to form the perfect country. Also, they did not kill a lot of their leaders. They merely wanted independence. The leaders of the time, as a matter of fact, did not even have a particular form of government in mind.