If the bio-medicals could come up with something that can treat addicts, that would be great, and I'm all for them trying to do that. Addiction is living hell. But, even if they did come up with a magic pill tomorrow, it wouldn't change a thing on the US/Mexico border.
The addiction problems you're talking about are found in people who use alcohol, meth, coke, heroin, ...drugs like that. The Mexican cartels are smuggling marijuana, not any of the others, at least not in large quantities. Marijuana doesn't have the same effect on people that the hard core narcotics and alcohol has on people. Treatment won't make a dent in the demand for marijuana because marijuana generally doesn't produce addicts.
Even if we did manage to eliminate demand for marijuana in the US, it wouldn't change a thing in the US/Mexico border region. The criminal enterprises operating there didn't just spring up recently, they've been there for a very long time, the region is now and always has been lawless. Prostitution, gambling, white slavery, kidnapping, organ harvesting, local drug demand, gun running, all of these happen in that region. There will always be a war between competing criminal interests in Mexico and in the border region no matter what happens with demand for illegal drugs in the US.
