Honestly, it's almost the opposite of a challenge (having the identity of the final boss public at the start). It's almost an easier way to tell a story and set up an expansion with a very clear theme, harkening back to the Wrath or Cataclysm/Deathwing days. We didn't openly talk about the end boss for some recent expansions because it wouldn't have made sense at the time, or it would have given away story spoilers and twists. For example, in Warlords of Draenor, if you were told you'd fight Archimonde at the end, it would have been a head-scratcher. But here, there is a major titan plus plus level antagonist that we are facing, and there are major steps in our journey to undercover the nature of the jailer's plan and put together the forces to have a chance against him. That story will wend its way through all of Shadowlands and our content updates, until we ultimately do get a chance to face the Jailer.