As late as possible. Early on, you’ll want to follow the missions in Battle for Azeroth right up until you get the option to send a follower on a two-hour long quest. As soon as you get there, stop doing the War Campaign missions. You can come back to them once you have reached something like 119 and a half and finish leveling with those if you want. If you don’t use these missions to cap off your leveling journey, then they’re the first thing you’ll want to do once you reach max level.
Discipline: Premonition - Heals nearby targets within 20 yards for [ 75% of Spell Power ], and applies Atonement to yourself. Deals [ PS * BC1 ] Shadow damage to yourself for each Atonement you have active, and increases their duration by [ 5 + 0.1% of Spell Power ] sec. Holy: Rapid Mending - Prayer of Mending is now instant cast, and its jump range is increased by 10 yards. Shadow: Void Origins - Void Eruption is now instant cast. Rogue
Excess Potion of Accelerated Learning: Acquired in your Garrison (part of the Warlords of Draenor expansion), this gives you a 20-percent bonus to experience from killing monsters and finishing quests. It lasts one hour, but you can buy it multiple times and use it back-to-back. Alliance players buy it from Sergeant Crowler, horde players buy it from Sergeant Grimjaw. Does not work above level 99.
We have no idea what implications this might have and whether or not it even indicates anything, since Patch 8.2 is still in testing and a Tuesday launch is more than unlikely due to Essence tuning and Azshara's Eternal Palace, which is supposedly coming shortly after launch. Blizzard said they wouldn't be delaying the new raid like they did with Battle of Dazar'alor.