The misdemeanor will remain on your record forever unless the law changes. There is no expungement for adult convictions in California. It sounds like you already obtained 1203.4 relief which simply adds the additional line of a dismissal to your record. Lobby the state legislature for true expungement although even if this occurs it is doubtful that said legislation would apply to the FBI (NCIC) record database. I regard the permanency of criminal records as an utter outrage but I regard it as a conscious and deliberate government policy that is unlikely to change. To the contrary, the general trend of government towards individuals - whether convicted of crimes or not - is to store as much information about those individuals and never to destroy that information. In the recent case of Maryland v King the court ruled that most arrestees, whether tried or convicted, can be DNA swabbed. That ruling may in the future extend to all arrestees and may eventually extend to all traffic stops. The government is unlikely to destroy that DNA information. Indeed the government has been creating massive store houses for electronic data (all data is electronic) and while it is unclear what purpose this information will be put to, it exceedingly unlikely it will ever be destroyed: http://www.wired.com/threatlevel/2012/03/ff_nsadatacenter/
The general trend towards the obliteration of privacy by government seems almost inevitable but it is not unless the public continues to be apathetic. Since you are directly being affected by this, you should do what you can to change it. Unfortunately nothing tangible can be done presently.
I'm not a CA attorney but to get your answer fast, you may benefit from using the cool "find a lawyer" tab here on AVVO to generate a quick "starter" list of attorneys ready to help. The tab is up at the top of your AVVO screen.
Best of luck with your search!
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Unfortunately, as far as your criminal rap sheet goes, it will never go away. For certain civil purposes such as housing and employment, California and many counties within California are increasing restricting the ability of landlords and employers to consider older convictions in the initial stages of the application process. I would look into both state and local implementations of the fair chance/ban the box initiatives to see if it helps you out. Good luck.