Really no way to tell. There are reasons why it would go up (people want to get high and will not face consequences) and reasons why it would go down (research and education on drugs will become more explicit and less interfered with by legislation, as well as more openness about drug problems which makes it easier for people to seek help if needed).

Who knows. No one. But keeping them illegal hasn't done anything to lower drug use, anyway. And I think the interests of personal freedoms and the issues of the black market should be enough to see why prohibition of substances doesn't work.

Agreed that there is no way to tell but I suppose peoples' mindsets might change, especially new generations growing up into a soceity where drugs are legalised. Drugs will be seen as acceptable and will definitely be more easily accessible, besides eduaction campaigns that might exist what is screaming out at them that drugs are harmful?

More drugs used, but not by a lot, and more responsibly used, with better quality and less death-by-bad-drugs, more facilities for those who want to quit drugs thanks to the billions++++++ in taxes collected, and less crime since it would no longer be in the hands of criminals.

All guesses. Good guesses though I think.