#1 - Oct. 6, 2020, 5 p.m.
The Shadowlands pre-expansion introduces a variety of changes and updates from character customization to the new starting experience.
The Shadowlands Pre-Expansion Patch is Now Live
#54 - Oct. 6, 2020, 10:55 p.m.
The drop rates of the mythic raid boss mounts won’t be reduced until Shadowlands so there’s still time to collect them. 
Feel free to refer to the Time Runs Short article for all the details of what’s going away and what’s going to be more difficult to obtain in the pre-expansion patch and Shadowlands.
Edited to align with the Time Runs Short article.