This is definitely a serious problem, I suspect that 7-OH-mitragynine, mitragynine pseudoindoxyl, mitragynine, carisoprodol, homegrown/extracted opium, relatively uncontrolled foreign opioids like tapentadol, and maybe phenibut/floribut/tolibut, cannabinoids, NMDA antagonists, or tianeptine are going to have to be peoples' substitutes for now.
I personally suspect that clandestine chemists are going to begin producing oxycodone in large amounts sooner rather than later, its synthesis starting from thebaine isn't trivial but it's certainly easier than a lot of other things.