It has been reported that earlier today 49ers offensive coordinator Mike Johnson signed with the UCLA Bruins to become their new offensive coordinator.
This move make sense for Johnson because he was likely to be replaced regardless since San Francisco signed Jim Harbaugh as the new head coach, and it is a common trend to bring in your own staff.
Following Jimmy Raye's firing after a Week 3 loss, Johnson took over and the offense improved. However, it is widely known that Johnson had a lot of work to do and was not very good on the pro level, at least not yet.
Going down to a college level will help Johnson get more play-calling experience in a lower pressure atmosphere.
It could be assumed that Johnson's overall goal is to either become a college head coach or be hired as an NFL coordinator again in the future.
As for the 49ers, it is unknown who will be brought in as the coordinator for the Jim Harbaugh era.
A hiring should come relatively soon, and as highlighted in the article linked above, Harbaugh should target someone with success developing quarterbacks and experience using the West Coast Offense.