We will come out with something else. I think we need to start working on phage therapy.
http://en.wikipedia.org/wiki/Phage_therapy
It's basically a virus that attacks a particular bacteria. It's totally harmless to everything else and self-replicates until the job is done. The only disadvantage is you have to have the right kind of phage for the particular bacteria you're targeting, which is why we gave up research when antibiotics came out and we could just shotgun it. I'm sure it'd already be available for things like MRSA and gonorrhea if the FDA didn't make it so burdensome to approve things.