The money coming from legal weed is building into a tsunami. Especially when local municipalities (Colorado) are receiving millions in tax revenue that is cash only. They don't want to deal with cash. With half the states having some form of legalization, the government has to do something.
The same thing happened with the end of alcohol prohibition. It wasn't all at once. But once the 21st amendment was repealed, the flood gates were opened for business. I'm not counting on it, but I'm definitely hedging my bets on it. Given these facts, I'd hardly consider it dumb to think they won't do anything.