As much as I would LOVE to see this happen, IMHO it never will. I say this for 2 reasons.
1: If the U.S. gov't legalized/decriminalized the use, posession, or sale of marijuana, they would be admitting they were wrong funding the marijuana specific portions of the "Just Say No" campaign. Can you think of one instance where the U.S. gov't admitted they were wrong?(Bill Clinton's apology for slavery notwithstanding)
2: The courts here in America have absolutely nothing to do with justice. They're profit centers. The lost revenue in the form of fines and NA/ASAP fees alone would be enough to kill the dream of legalization forever.