The criminal element will still be the criminal element, they will find other crimes to commit. These aren't people who want to work hard for a living, they want the easy money and they are attracted to violence. Already many of the Mexican drug cartels have included plenty of other crimes like extortion and kidnapping for ransom. The last thing they'll do is clean up and flip hamburgers for a few measley bucks.
But no money is easier than drug money; removing the big profit margins from that trade will at least give criminals less money to buy weapons and present a flashy lifestyle that lures others into crime.
But when vices are treated as such, not as crimes, the crimes that are left are those very few people are sympathetic to or apathetic about.
I have a lot more antipathy for a burglar than I do a kid selling weed in the park.
As a minimum, I want every burglar caught before police time and effort is wasted on vices. We're pissing away gazillions in the WOsD. We're criminalizing hundreds of thousands of citizens who have violated no one's rights. Corruption is rife in our police forces because of the cash. Individual rights are being swept out with the trash as SWAT teams conduct no-knock raids that kill and injure innocent citizens.
As another poster said, the War On Drugs is the worst set of policies ever enacted in America.