>a new person takes over as leader of the vanguard.
Let's face it, Zavala is over, he's not even a Guardian anymore. Ikora is of course the perfect candidate but the Ikora fatigue is real, we are seeing her everwhere/time since the Witch Queen.

Do we still need the Vanguard? We won, we Killed the Darkness, we saved the Traveler, we destroyed once and for all the Vex, the Fallen houses and the Red/Shadow Cabal.