Well, for starters, the current rush of patients away from doctor-prescribed and monitored opioids to street-supplied heroin and fentanyl would slow down dramatically. If I could get 10 to 30 codeine/aspirin pills a year from the pharmacist, like Canadians can, I certainly wouldn’t consider street drugs.
(Which would mean far, far less money flowing to criminal syndicates with a history of murder and intimidation and political bribery. That’d be a nice side effect!)
But as one of the articles I linked points out, Portugal did more than just legalize. They also instituted serious harm reduction programs of many kinds, and treated addiction as a medical problem rather than a social one. We can do that for less money than we are currently spending on failed drug wars and failed childhood indoctrination programs.
I believe that if we follow a process similar to Portugal’s, we’ll see things start sorting out in ten years or less, as they did. Whereas if we continue as we are, instead of plateauing, and then decreasing, we’ll see continuing increases in overdose deaths and drug related crime.