Even if such an agreement worked in principle - which I don't believe it will; the resistance genes will hide out somewhere and re-emerge on short notice upon resumed drug use - how do you enforce it? More to the point, how do you persuade a doctor not to treat that patient suffering in front of him right now, just so that a hypothetical, statistical advantage might accrue in the future to persons unknown? 

Selectively killing bacteria is, and remains, an easier problem than selectively killing tumor cells. The problem is it doesn't pay - treatment typically lasts some two weeks (though longer with TB and a couple of other diseases). Because of that, accountant-run drug companies continue to divest themselves of their antibiotic research units, focusing instead on drugs that patients will take for the rest of their lives (hypertension, lowering cholesterol etc.). Even mere pipe dreams such as "curing Alzheimer's" attract more research dollars these days than antibiotics.