I'm not going to claim to be able to predict the future, but it wouldn't surprise me if the federal government stampede all over Washington and Colorado's states rights in terms of legalization. A lot of people don't like the idea of recreational cannabis use, even if a lot of these people believe medical marijuana to be totally acceptable.
Furthermore, California already has a very well developed medical marijuana industry and most people who want to get jobs with medical marijuana go to California. Washington and Colorado have medical programs, yes; but I doubt the volume of sales, production, and employment is anywhere near what it's like out here in California.
As a last point, I wanted to say that California's medical marijuana system has been around for some time now. It's not impossible that Colorado and/or Washington may get rid of their legalization efforts. Montana had a medical marijuana program, and they got rid of it. There was even a vote to bring it back - and that vote failed, miserably, namely because to bring back medical marijuana you were supposed to vote "NO" on the proposition. I wouldn't be surprised if a group of people are working right now just to nullify Colorado and/or Washington's legalization efforts.