I'm sure it's the lack of mandatory grinds that makes people quit the game, not the 7-9 months of no new content...
@Topic:
let old content be old content. This idea to turn a raid into a dungeon so that it stays relevant can only come from someone who isn't actively raiding every week. Because after half a year of Nathria the last thing an active raider wants is to keep going into Nathria.