I don't think that's going to happen. The best you could get is (IMHO) that most drugs are about as legal as morphine, or vicodin--that is, allowed for medical use but nothing else. Of course, there will be plenty of people abusing that, just like OTL. More likely is having some of the "soft" drugs stay legal, some of the "hard" drugs become illegal, and the rest either ignored or semi-legal as the above.