That sounds interesting, but somehow not like a normal gate event? Or maybe it's like others said, that SDs will be replaced with Rare Hunters that give you whatever item you need to duel him at the gate. (Bring it on, Steves.)
That's what I thought too, but it doesn't seem like that's going to happen now. Maybe Marik appears once the Yami Marik event is over and his evil self is defeated (or so). This could also make sense but would probably be a spawn event only and not an unlock event (for now).