The Dragonflight pre-patch interestingly has 2 splash screens, which could hint at pre-patch events starting at a later time.
Splash Screen 1 Text
Text in the first splash screen mentions UI updates, Dragonflight’s release date and the new talent system.
New in Dragonflight Pre-Patch!
User Interface Updates – The UI has undergone an art refresh. Customize it with the new Edit Mode!
Dragonflight Coming Soon! – November 28
New Talent System – Explore the brand new class and specialization trees and create your own talent build!
Splash Screen 2 Text
The second splash screen talks about the pre-patch events — Elemental Invasions and Uldaman returning as a Level 60 dungeon. It also mentions Dracthyr Evokers being available for play.
New in Dragonflight Pre-Patch!
Tempest Unleashed – Vanquish powerful elementals in storms that have erupted across Azeroth.
Uldaman – Brave the perils of Uldaman to secure the future of dragonkind.
Dracthyr Evoker – Azeroth’s newest race and class has awakened. Wield the power of the dragonflights to deal damage or heal your allies.