I live in the Victoria and there are about 30 cannabis dispensaries.  I've never been to one but they seem to be doing good business.  Which shows that many cannabis users will forego the black market if the product is available in even a semi-legal way.  I was downtown the other day and was struck by the fact that no one on the street asked if I wanted to buy any "weed".  Even walked by the places the dealers used to hang out. Nada.
In addition, I have a friend who has made his living selling pot to adults for the past 30 years.  He says business is drying up already due to the dispensaries and that he will be out of business by the time pot is legal.
I'll continue to grow my own in my fenced, secluded back garden, not drive while impaired by anything and try to mind my own business.