I'd guess that in the next twelve years, one state will finally be the first to legalize it. Of course the inevitable will happen and the feds will move in to shut it down. Then the state will sue and it will become a long ugly court battle that will eventually end up in the Supreme Court. The Court, depending on its makeup will have to decide a number of things (medicinal value, how that states law applies towards the commerce clause, or if it is a states right issue). So, who knows if marijuana will ever be legal because it could be decided by a court decision that will establish precedent.