It's probably nothing, and just a coincidence. But the Chromie Timewalking Campaigns UI panel is designed to fit exactly 9 expansion pack thumbnails, and it currently has 8 in it. In the bottom right corner, there's a gaping hole likely meant for Dragonflight.
Like I said, it's probably nothing. But it's interesting to think that it might mean something happens after Dragonflight, such as a revamp and a "soft reboot" to WoW, meaning there won't be future expansions to place inside this interface.
For example, in the event of a revamp in 11.0, they might switch to a different type of model for new content. Annual mini "expansions"? DLCs? Simply adding more and more content to the revamped continents?