Well, it's probably going to go one of two routes.
Simplest route is to do everything all at once, decriminalize, legalize, regulate and tax. This is probably going to take a long time, at least a couple of years, because all the appropriate regulations and laws need to be written.
The 2nd route would be to first decriminalize it (which would be relatively fast), then to legalize, regulate and tax it. This would take a few months longer, but it would be decriminalized faster which is nice. Not sure which route he's gonna take...