I think short term it would just fucking destroy them. Power shifts, etc.
But what becomes their next gig? The ultimate goal is weapons and money and land, so they need a commodity to acquire those. It needs to be something that cost little to acquire, and sells for high dollar on the other end. If pot really is 60% of their income, they are going to be in a hurry to replace it, if the market does indeed collapse around them because of legalization, which I think it would. Their weed sucks. I don't know who is buying all that shit making them rich but it isn't me.
My bet is they ramp up human trafficking. Pot is an easy sell, I don't know if they could push other drugs successfully enough to replace their pot sales. But humans, either to fuck, torture, work or kill....there's never enough of those when you need them.