If this change were to happen, what would happen to the state-regulated marijuana industry?

ATACH does not  anticipate a significant change to state-regulated marijuana markets from a rescheduling from Schedule I to Schedule III alone, for several reasons: 

• FDA already has regulatory authority over marijuana, THC and CBD, and Schedule I to Schedule III does not increase or diminish FDA’s current authority or discretion in regulating state-level marijuana markets. 
• To the FDA, the entire marijuana market (including medical marijuana) is not federally legal, and for all intents and purposes, is only interested to the extent that the agency safeguards public health and safety. While it has statutory regulatory authority over cannabis, it has not intervened except in a narrow set of circumstances. The state-regulated market operates completely outside the pharmaceutical drug, food, and supplements programs administered by the FDA and DEA, and that is unlikely to change due to scheduling from I to III.  
• FDA has limited resources for even its current responsibilities, and in order for FDA to be more involved, it would need additional funding from Congress or a significant change in federal law such as the passage of adult-use legalization. 
• It is hoped that Schedule III would open the door to more research, and there  may be more interest by pharmaceutical companies in pharmaceutical drug formulations, but pharmaceutical companies could have sought those formulations without a change in the scheduling and this FDA process for investigation of new drugs will not change due to  scheduling. 
• Perhaps most important to state-legal marijuana businesses, Schedule III would remove 280E taxation that the IRS is currently misapplying to the cannabis industry.