Correct me if I'm wrong, it is not the first demonstration against him. Something like 5 years ago people were not happy for him going on a second term.
As for "revolution", unfortunately such events doesn't go well in post soviet countries. In all previous cases new government was way worse than the previous one.
You are right about the demonstrations. There was a number of big protests in Armenia in the past, none of which brought any significant changes.
As for revolutions, generally I agree with your point and understand your skepticism. However I can bring up the Rose Revolution in Georgia as an exception to the rule. Rose Revolution brought peaceful transfer of power. The people who came into power after that practically eradicated corruption in the state. They liberalized the economy, and as a result of their policies their GDP went up 300%.