Lets be real, as much as the end to thw war on drugs is being painfully slow, its coming eventually. I frankly think the war on drugs has been the single most harmful American policy since segregation too, but thats besides the point.
Anyhow, lets start with marijuana, since that is the only drug we have made any federal progress on really (hemp legalization and banking only), and the only drug states have legalized.
Anyhow, I suspect what is going to happen with this on a federal level is some time in the next four years we will see the feds stop dealing with it at least. I am not hopeful the feds will mandate legalization in all states under a biden administration, but at this point the amount of states with marijuana programs that do not align with federal law vastly outnumber the States in compliance, so we may see something like the STATES act pass soon (probably not for the next two years though tbh) which exempts marijuana from the CSA either federally or from a federal standpoint in legal states. For the average user, all this would mean is you can now order it in the mail perhaps if you are in a legal state, you can legally bring it across legal states lines, and you would not technically lose your firearms rights the second you buy a joint unless your state says otherwise. From a distribution standpoint, this would probably mean big interstate cannabis conglomerates may be able to form, which while shitty, means that it will be able to lobby states into legalizing much quicker, although expect some big tobacco level control of weed as a result of this in the coming decades.
overall though, much like the end of prohibition, I do not see the feds mandating states legalize it for decades to come if at all. So if you are in Alabama, you may be out of luck for a few decades still until big marijuana gets big enough to lobby otherwise, but I think most States will be legalized in 10 years, and the illegal states will be the exception not the norm.
Now, other drugs is where I think we face a larger uphill battle. Currently, the only progress we have really made so far is Denver decriminalizing mushrooms, a town or two in California deceiminalizing psychedelics, and a police department in Pennsylvania refusing to enforce any drug laws (the cop behind this very well may be my only exception to ACAB). We have nothing on a statewide level, let alone national level, for any other drugs.
However, I think this year may mark the first year we make some serious progress at least towards general decriminalization, as Oregon is slated to have a ballot initiative in the 2020 election, which if passed, will decriminalize possession of all drugs within the state, and Washington DC also has a ballot proposal to decriminalize some psychedelics (The Oregon proposal is much more important and is a much wider scope than the DC proposal, which can be overruled by Congress, and only makes it a "low police priority" and asks the DA nicely to not prosecute).
Sadly though, I think we are going to basically be starting back at square one with all other drugs just like we had to with marijuana. It will likely be many decades before we see anything federal, and even then it would likely just be a STATES act for all drugs on the CSA or something, not federally mandated legalization.
in the meantime though, what I suspect we will see with the legalization of other drugs is some states decriminalizing slowly one by one, with medical programs slowly being introduced for things like mushrooms, mdma, and LSD, which eventually morph into recreational legality in certain states like we have seen with marijuana, which, after decades, will probably create a states act situation like we are on the verge of with marijuana. Psychedelics will eventually be legal in all 50 states probably, but expect it to take a similar amount of time it takes for weed to be legal in all 50, so it may sadly not be in your lifetime.
What about genuinely harmful drugs like Meth though you may ask?
Eh, hate to break it to you, but I doubt you will be able to buy that stuff legally in your lifetime, dont get me wrong, it is unlikely to remain a criminal offence to possess in every state or even federally depending on how the psychedelic states act is written, but at the same time I don't see a path beyond decriminalization for these types of things right now. They have next to no medical value given we already use legal version of this stuff for prescription drugs, and recreationally these types of drugs have clearly been shown to cause more harm than good. I don't think we will be locking up meth dealers for decades like we always have forever though, because I do expect we will have some more general criminal justice reform as well, but overall I don't really see a path forward to "meth dispensaries" whatsoever right now.
For the legalization of all drugs, period, Maybe society will be ready for that in like 70-100+ years, im not sure, but I don't expect to see that any time in my lifetime in a broad manor in the United States, and I can not even attempt to predict what the path forward for that would look like given the current information and situation.
That being said, I care far more about psychedelics than legalizing meth.