The main revenue will be from the money saved from law enforcement since a lot of police won't be needed anymore if communities decide to legalize it. The money saved is forecasted to be more than the tax revenue.
ack-ack
Ack-ACK
on this assumption i believe you are partially inncorrect. the idea that there will be need of fewer police of any type because they legalize marj is inncorrect. marj is never the sought after drug hunted by the police DEA FBI etc etc. they only bother with weed when they find it by mistake or when they believe that the person they intend to arrest for it can provide information on much bigger crime/drugs i.e. coke heroin guns murder etc. if they legalize marj then they will still need the personal they currently have to continue looking for the issues that are considered truly severe.
oh and before you mention "well what about the growers"? they only seek growers because growers have connections, it is those connections that they are truly after not the grower him/herself. bulk growers need shippers, those shippers tend to work for more people than just the growers. they work for people who need to move hard core drugs guns and any other illegal substance. oh and even weed dealers need accountants to wash their money, a good money launderer is worth his entire families weight in gold to both cops and crooks.
so my point being that the legalization of marj will not put the slightest dent in the amount of law enforcement officers required. it may cut down on some tiny percentage of court cases, so there will be some savings there, but not much.
oh, and one more thing that people tend to forget/intentionally ignore.
just because something is state legal DOES NOT MEAN IT IS LEGAL!!!!!!!!
the federal government supersedes all state and local laws. the feds are entitled to enforce their own laws even if those laws are in direct contradiction of any local or state regulation. if the feds don't legalize it then you are still at risk possessing and /or using it. granted it wont be much of a risk, but it is a risk that a person should make them selves aware of.