I think that is what everybody is waiting for. I read in the article that it could take a year or two before FDA fully approves and then mandatory is easier. Right now we are under an emergency approval which doesn’t have the “teeth” enough to make it mandatory at least at the government level. Of course, private owned places are dipping their toe in to mandatory vaccinations. The courts will certainly be involved when someone at a company or school sues.
https://www.google.com/amp/s/www.latimes.com/opinion/story/2021-03-14/could-covid-19-vaccines-be-mandated-federal-law-nee%3f_amp=true