I have a couple years of phage research. Unfortunately we haven't really seen phage-attacking viruses yet. I know the "first known virovore" made its rounds here a while back, but in the case of a phage attacking another virus, neither really has a "metabolism" to exploit.

Your point about bacterial resistance to antibiotics vs phages is almost correct; increasing resistance against one attack broadly tends to decrease efficacy defending against the other, though as I am not familiar with the mechanisms for this, my uninformed hypothesis would be that the gene expression required comes at a high price - you can't defend against antibiotics and phage and outcompete your Petri-dishmates.

I suspect that for the future, medicine will be antibiotics in combination with phage cocktails of several phage strains that sabotage in different ways (targeting capsular polysaccharides vs surface proteins vs flagella, for example), to prevent a repeat of antibiotic resistance.