I still think a lot of people will grow their own, so long as it is allowed. It isn’t that hard to grow hydro but I doubt you could do it efficiently enough to make it worth it. But you can grow perfectly good mid-grade weed, very easily.
I really think, if this passes, we will see the rest of the states fall like dominoes. Those states neighboring California will see their residents crossing state lines to buy and they will resent the lost opportunity of the taxes generated, will have virtually no way to stop the flow and will then move to legalize. It will go like Lotto did, but even quicker as the states without lotto were not spending money trying to stop the tickets.