There would be (likely) some more people who used them. At first.
There would be (likely) some more people who, having used them, developed addictions to them. A few.
The already-corrupt pharmaceutical industry would clean fucking house with the insane profits they'd be able to rake in on generic cocaine. For a while.
But
letting things go as they are right now is really not a good idea, which was obvious 20 years ago.
Oh, and another small downside: we'd (possibly) have to admit to our own blindness and hypocrisy in pursuing this illusory "war" on drugs, which is really a two-pronged war, on liberty and on pleasure. Neither of which seem to have been remarkably reduced by it.
We need to say "uncle" and declare the war on drugs a loss, and get on with building a just, free, and joyous society, resting on the principle that (most) people can decide for themselves what is good for them, and what pleasures (and vices) they decide to seek out and which ones they choose to avoid. Because let's be honest: we are all grownups now, and most of us do not appreciate being told we are not mature enough to figure out whether we need to use some ice, an aspirin, or a 12-hour extended-release Vicodin.