A ban doesn't mean that something stops, a ban means that it becomes extremely difficult, a punishable crime, and the risk-to-reward ratio becomes significantly diminished.
Likewise, the inverse is also true. CB radio was illegal in the UK, but it was hugely popular, then, overnight, upon it being made legal, it died. Most people lost interest because it was no longer exciting. You see the same thing with legalizing cannabis. Sure, you'll get hardcore consumers and enthusiasts, and people using it for medical reasons, but it's no longer cool/edgy/interesting, and when it is so accessible.
Could really go either way, but when it comes to money, people don't tend to fuck around.