There's nothing I can disagree with. But SM holds grudges so will they let RV come back or will it be like GG and take 5 years?
I could see it going either way, tbh. Part of it is coordinating schedules of 8 different idols, and the three who left first each went into things that would be hard to coordinate around (Sooyoung and Seohyun who focused on acting, primarily TV shows which have a long time commitment, and Tiffany, who focused on trying to enter the American music market). So it's possible that RV comebacks could slow down to once every 2-3 years, but not be as infrequent as SNSD's "for major anniversaries only" schedule that they seem to be on.
But to be a teeny bit fair to SM, they did also do Oh!GG the year after the three didn't renew, so in our hypothetical, only Irene & Seulgi stay behind, it's possible their subunit gets another comeback (which they should anyway, with how well that did).