I posted on this topic a few months ago, so if you search for "RJs in San Diego" you might come up with the previous thread. The gist: No word on RJs any time soon. They are currently being deployed elsewhere by the airlines. The only commuter airlines operating at SAN are Skywest for United and American Eagle for American and Delta. United flies perhaps four 737s daily to LAX. Many airlines have operated the route over the years but we're basically left with United.
Personally, I'd like to see RJ service to destinations like Yuma or Fresno from SAN, as well as frequent LAX flights.