You seem to believe that a move from Schedule I (totally illegal to sell) to Schedule III (legal to sell under some circumstances) is going to hit the reset button on state laws around cannabis. That seems unlikely, the states are already ignoring the feds on this, this is just a step the feds are taking to bring the federal legal landscape closer to the state landscape. The major changes will simply be, as others have stated, to make it possible to travel with cannabis (with an Rx) and for dispensaries and others to use FDIC insured banking and transfer mechanisms.

Other than that, nothing is likely to change unless states walk back the laws they've already passed.

Remember, it's already illegal on the federal level for these businesses to exist, and that isn't stopping them.