[Update]: After a fair bit of testing, Shadowlands' quality-of-life focused Update 9.1.5 has now arrived onto the live servers.
Out of all the new additions to World of Warcraft over the past couple of expansions, Legion's Mage Tower is definitely at the very top, right alongside the always popular Mythic+ dungeons. The reason this is the case is quite simple. Mage Tower offered challenging end-game content targeted at both casual and hardcore players, with the end reward being some of the most beautiful class-based cosmetics WoW has seen in years.
With that in mind, I have both good and bad news to deliver. The good news is that the Mage Tower is not only coming back as a part of Legion Timewalking, but that Blizzard will be adding a whole bunch of new class-based armors to it, as well as a spellbook mount for those that manage to beat all of the challenges.
The bad news, as you might already guess, is that they will be removing all of the immensely popular weapon cosmetics in order to keep them exclusive. Interestingly enough, the one exception here is the Guardian Druid's 'werebear' form as that will be getting a new fel variant for everyone to obtain.
Sadly, there's one more bit of bad news, and that is the simple fact that the Mage Tower will only be available during Legion Timewalking events. Once patch 9.1.5 releases the Mage Tower will remain open for two weeks, after which it will go to its usual schedule of being open for one week every four and a half months.
Needless to say, I'm not a fan of how this is being handled. Not only do I believe the old weapons should be available for everyone because locking away such awesome cosmetics is a silly thing to do, but I also don't like how infrequently the Mage Tower will be open.
Having it be available for only one week every half a year means that anyone who's interested in it will essentially have to force themselves to play it and it alone for extended periods of time in order to collect the sets they want, and especially if they're aiming for the spellbook mount. It just seems like such a waste of potential for what could've been a great way to keep players entertained while World of Warcraft suffers from a massive content drought.
Whether you agree with me or not, you can read more about Blizzard's plans for the Mage Tower, as well as offer your feedback, over at the World of Warcraft website.