(X) Doubt.
More likely, people will run it once every 3 weeks when it comes up in the Fated rotation. And Blizzard is going to bring the raid down in difficulty to roughly match the other raids. We’ve probably got 4-ish months left on this raid, which means Blizzard needs to tune down some of these bosses so folks can get their CE since it won’t be an 8-month tier like 9.0 / 9.1. Seems to fit.
Nah. The game would take a huge hit but if they switched to M+ as the main focus of the game the game would still go on. In fact, in the twilight of this game I expect that to happen, for them to wind down from designing new raid content to focus on seasonal content. New M+ affixes, reshuffling the dungeon roster, etc.