Governments around the world should think long and hard before legalizing it because as soon as they do, people will move to the next thing. Maybe something that it's both illegal and won't cause much harm such as cocaine and party drugs. Still more harmful than pot though.
For sure there would be a sudden spike if you could buy pot at Whole Foods, but I'd be surprised if 1 year after legalization there are huge differences vis-a-vis the current regime
The way I see it , alcohol is the layer0 . People use it to lower their own inhibitions and also groups as a whole to lower the group's inhibitions.
Once a substance that can perform the aforementioned function is provided and legal, everything else becomes a contest for people trying to one-up each other.
And I think pot is included in it, but also cigarettes and all the other drugs.