On November 4th, Proposition 47 was passed by California voters. Prop 47 reduces many non-violent drug and property crimes to misdemeanors. Importantly, the change is retroactive, meaning that people who have previously been convicted of a felony for one of these crimes may be entitled to have their conviction reduced to a misdemeanor.
People are already being released due to Prop 47:
http://thinkprogress.org/justice/2014/11/07/3590167/people-are-already-being-released-from-detention-because-of-californias-ballot-initiative/#