Disagree with all this "Legion is just as crap as every other xpac" talk. Sure raids haven't opened up yet and could be a giant flop, but I was bored to death within a few days of hitting cap in WOD (I did enjoy the levelling experience initially, which is more than I can say for MOP), let alone weeks, with literally nothing to do but run each heroic every day and set up garrison crap - only reasoned I stuck around long enough to check out Highmaul was that a lot of my friends were also playing at the time, and I quit within a week or two of starting that. MOP was so awful I ended up levelling 87 - 90 entirely through dungeons while watching TV because the open world content was so dull. LFR'd each raid a few times then promptly quit out before it made me gouge my eyes out.
Legion, meanwhile, has had me glued to the game since it came out. Pretty certain I literally haven't opened another game this whole month.
Is it perfect? Of course not. But I've been playing maybe 3 - 6 hours a day since it came out and haven't logged off a single time thinking "man what the fuck did I waste that time for?" Every session has had me encountering something new, making progress with my character and feeling engaged with the game, and I haven't even touched any of my alts. I've only just started feeling the urge to watch TV or listen to podcasts while playing, which is usually a good metric for when things are starting to get repetitive.
It's gonna get old eventually, everything does, but this is easily the most detailed, engaging and content-rich iteration of the game since Wrath/early Cata.
As for the subject at hand, only thing I really care about is Metzen leaving, since I love the older lore - but as people have pointed out, he's been phoning it in hard the last few years, so maybe fresh blood will be a good thing. It'll be a shame if this means there are no more Warcraft Chronicles books though