Hello, yes!
“To celebrate this anniversary in style, we have prepared numerous activities and events for you. If it is not declared otherwise, these events are temporary and will take place from January 7 to February 8, so do not miss this opportunity. Some of them will also be permanent, however, and can be enjoyed beyond Tibia's birthday.”
The time travel cave and boss Lord Retro are permanent additions to the game.
https://www.tibia.com/news/?subtopic=newsarchive&id=6429
In Fórum, Skerio answered the following question:
Also can you clarify if the Time dungeon and Lord Retro is for every anniversary or it will remain in game even after the anniversary for example in March it will be there?
The latter, they are not bound to certain dates.
https://www.tibia.com/forum/?action=thread&threadid=4901013&pageitems=20&pagenumber=19