I imagine the long term solution to antibiotic resistance are engineered bacteriophages, either to directly attack the bacteria or to insert genes that make the bacteria susceptible to specific agents. Beyond not having to continuously develop new antibiotics or restrict treatment, these could also be much more targeted treatments with less harmful effects on a patient's microbiome. Of course scaling up to mass production on the level of say penicillin will take some time, but the same is true for new antibiotics.