The problem Halloween has is not keeping new legacy characters once they develop a following. They kill them all off almost immediately, so there is no cat and mouse story for the fans to follow. This is why Jamie Lee Curtis has always enjoyed a periodic paycheck from the franchise, because her character has hung around since day one. Thats also what has kept it from being completely one-note in its delivery.
Look no further than Resurrection and you understand what happens when the story is adrift after you kill off the last remaining legacy character. Once Laurie Strode was eliminated, it literally took the air out of the rest of the picture. Where are the stakes? Who cares about these new characters that will all be victims anyway? That’s the problem. And thats what will be a major challenge for the studio for a 50th anniversary chapter, because they have exhausted the Laurie Strode saga. Who would want her back in six years? The only legacy characters left untouched is Rachel and Jamie. To tell a completely foreign story with no legacy characters in it for the 50th would be a bad miscalculation.