I give it 50/50.
Here's the thing. People have this vision where everyone will be able to use pot and function in normal society, and it won't be a thing anymore. That's not going to happen. As pot becomes more 'legal' in society, businesses which have a strong interest in protecting their reputations and shielding themselves from liability are going to lean into enforcing HR policies banning pot. Meaning, instead of just testing upon hire, they will have more random testing to enforce policies. It will feel more like the military. "I would have a doobie this weekend, but I don't dare, because I might have to pee in a cup Monday morning."
Imagine that there is say, a construction company that has a tractor roll off of a construction project and causes an accident. They try to shield themselves from liability, and a former employee makes an accusation that everyone he knows who works there smokes pot. So they test everyone, and the driver pops hot. Now they are looking at liability. Then rival companies start to advertise; "We are clean and reliable. All of our employees are background-tested and drug-checked. Not like those other dirtbag companies that kill people." It becomes a purity contest. The workforce will separate into what I am going to call "Green-Collar" jobs. If you want to smoke pot, you will have to work in sales, call-centers, service sector jobs like restaurant servers. If you work in any industry where businesses face liability for people being high, you can plan on enforced no tolerance policies.
I can see incidents where someone is involved in a defensive shooting, and there is an abundance of evidence they were a pot user. Since it is difficult to discern whether they were actually high at the time, but they CAN determine if they have THC in their system, that becomes the default standard for liability. You use pot, and someone got killed. You are liable. Alcohol is easier to state whether someone was under the influence at the time of the incident.
Not saying it's right or fair. I do not pretend to be the great and powerful arbiter of these things. But I don't believe for one second that we are just going to legalize pot and that will be the end of these questions.