If you don't take antibiotics for pneumonia, do you either get worse or stay plateau?

Worsen/death: bacterial pneumonia is still a major cause of hospitalization, morbidity and mortality: antibioticsd are mandatory.

Depends: Pneumonia is a label that can be used to describe a self resolving viral illness or a bacterial disease that is often fatal if untreated. There were occasional survivors of bacterial pneumonia in the pre-antibiotic era, but it was a rare event. Most died during the acute illness or from complications after an apparent plateau. It is a common cause of death in the undeveloped areas of the world