Boosters will almsot certainly be approved for everyone once we get a little further along and the shots can be tailored like the flu shots are per season.
That is is presumption based on the efficacy continuing to decline, which it might not. We'll have to wait for the data to confirm that.
Before we get to boosting the original vaccine formulas, there may come a variant that escapes the current vaccines. In that case, we don't need a booster, we'll need a new vaccine formulation and everyone will need to be re-vaccinated. (Of course, a booster from the old formulation can be added to the new formulation so that the original variants don't reappear).