For example, as a purely hypothetical example, if given a choice between the government expanding the current FM band
Never happen. Hundreds of millions of radios currently in production wouldn't be able to receive the station.
AM and FM are going to start exactly the way they are until true universal free wireless internet is the norm. No dead spots. We're 40 years into wireless phone technology (15 years into the really advanced part of it) and we still have large portions of entire states that have no coverage.
If I had to bet, radio will be alive and kicking at the beginning of the 22nd century in some form. This country is too massive to just have everyone stream everything.