Through the Ages: New Leaders & Wonders, the new expansion for Through the Ages, has been delayed until February/March next year. The publisher CGE has posted an update on BGG explaining the reasons behind the delay:

The card printing problem that led to the original delay last month is more difficult to solve than we expected. As a result, we hope to have the game out by Spring of 2020, but we can’t be more specific.
(Source: BGG Forum)
The problem we are trying to solve is that the card backs for the expansion look different than the card backs for the base game. This means players can make out how many expansion military cards their opponents have, or see whether the next prepared event is from the expansion. This is not information players should have.
We apologize for the delay this is causing. We would not be postponing the game’s release, however, unless it was to ensure that every player of Through the Ages and its expansion has a good experience.
If you have an order in place including the expansion that is now delayed, please contact us.