This should be in Toke and Talk or Politics section but to answer. No. The market would thrive, but small grow ops would suffer most and with everything else in this country the market will be cornered by the large powerful companies and the only war of prices would be between them. Overall, prices for users would drop, at least at first.
The important thing to remember is, it will never be "fully" legal, never. I mean never. I can't make that point clear enough. Never.
I think medical and decriminalization will expand some, but that will have no or little effect on prices. On a federal lever medical would be the only area legalized. State by state we would have different decriminalzation laws, but fully legal marijuana is not in the future of America. I'm all for it, as many are. but the forces against it are far more rich and powerful then we are.
If legalized there would be just as big of chance as General Mills selling weed as would the tobacco companies, which really have nothing to do with anything positive in supporting the legalization of marijuana.
I just don't think legalization will ever be a serious and legit argument in this country. Even medical is having problems progressing with constant raids and opposition rising again it. If the people in charge don't want people dying of cancer getting high, us regular users sure as shit ain't being considered. Romney would outlaw weed from existence if he could, but my main concern being Obama will win his second term, is where the hell will he stand on this issue after the election? He has done nothing positive for the marijuana legalization movement his entire admin, no reason he would start now.