Well, there is an argument to be made that once it is fully legal more people will be drawn into consuming cannabis. Especially once the health benefits start to be recognized, so demand probably will increase.
But a glut in supply won't easily be absorbed since it is a perishable product. Someone will literally get stuck holding the bag.
California is about to go through it's own bubble burst. They have brought thousands of acres into production in the past year alone and once these crops make it to market, you won't be able to give B grade weed away (kidding here, but $50 a pound could happen); same for any crop that didn't sell last season.
Eventually, enough growers will drop out to stabilize the market a bit. But compared to growing tomatoes or cucumbers, even $10 a pound at wholesale is a killing to some farmers. Investers, not so much....