https://www.polygon.com/2018/7/13/17568938/battle-for-azeroth-pre-patch-world-of-warcraft-release-date-features

The era of Legion is coming to an end as World of Warcraft: Battle for Azeroth’s arrival approaches. Next week, on July 17, the Battle for Azeroth pre-expansion patch will be released. Not only will the patch remove some old content, it’ll also update the classes and add new quests for players to experience before Battle for Azeroth’s release.

When the pre-patch goes live, all of Battle for Azeroth’s class changes, overhauls and rebalances will be updated for the live server. To compensate, the Legion Artifact weapon traits will be disabled, leaving players with a normal stat-stick to hit things or cast spells with. However, players will be able to transmog any weapon into their old Artifact — as long as it’s the same archetype.