All we know is that CBS/Paramount have made no official statement about another show other than SFA. "Legacy" is and always has been just Matalas's pipe dream that overactive fans have taken to be some sort of gospel. Does that mean that CBS/Paramount is not interested? Beats me, because like I said, they've mentioned nothing about it. If I had to guess, I'd say they have no intention of making a follow-up to PIC, because it's probably beyond their budget.
How many years has it taken to bring SFA to series? (It was first mentioned in 2018.)
Section 31 went from from series to streaming movie.