There was a very robust underground for liquor sales during prohibition but it died out pretty quick post prohibition.
There is a difference though - the liquor industry was long established before Prohibition, and Prohibition lasted a relatively short period of time. All the while the industry kept functioning outside of the Prohibition areas, and was ready to step back in when it ended.
Marijuana never got to be an established industry like alcohol before it was prohibited. I suspect that given the suggested pricing differences and current black-market availability that the latter won't go away overnight, but there will be a decline in favour of the legal market.
I don't think it will come from busting more heads, but rather adjustments to the legal market to squeeze out the illegal market.