"Heroin abuse is a big problem that's only going to get bigger in the US. With legal weed, a lot of former marijuana producers are getting wise and starting to farm the opium poppy. Plus a lot of folks got addicted back when Purdue was pushing Oxycontin, and now that it's harder for them to obtain they've switched to the cheaper and more potent stuff."
I'd really like to see some numbers on this.
From what I understand, there are far, far more marijuana users than there are heroin users -- like many orders of magnitude more. So, yeah, illegal marijuana growers could certainly switch to growing opium, but they're not going to magically get anywhere near the number of customers.