Bernie Sanders got the Democrat platform committee to include this language in their platform.
Because of conflicting laws concerning marijuana, both on the federal and state levels, we encourage the federal government to remove marijuana from its list as a Class 1 Federal Controlled Substance, providing a reasoned pathway for future legalization
That is pretty thin gruel. Maybe Trump will make a better offer. I would expect that Trump will do something about a week or two after he gets nominated. I think some time around the beginning of August would be good. If he was to do it at all.