It does not look like it is on the Pokemon site yet, but inn the PokePortal it has been announced that Walking Wake (Scarlet) and Iron Leaves (Violet) will be returning to Tera Raid battles starting 25 December at 00:00 UTC until 07 January 23:59UTC.

You can only catch them once per save, and if you have caught them in previous events you will be unable to catch them this time around, but cannot still participate in the battles. Walking Wake will have a water tera type, while Iron Leaves will have psychic tera type.

From Home:

From Monday, December 25, 2023, at 00:00 UTC to Sunday, January 7, 2024, at 23:59 UTC, Walking Wake will be appearing in 5-star Tera Raid Battles in the Pokémon Scarlet game, and Iron Leaves will be appearing in 5-star Tera Raid Battles in the Pokémon Violet game.

These Paradox Pokémon cannot normally be encountered in Paldea. The Walking Wake appearing during this event has Water as its Tera Type, and the Iron Leaves appearing during this event has Psychic as its Tera Type. Try joining Tera Raid Battles hosted by Trainers playing the other version of the game to help complete your Paradox Pokémon collection!

The special Walking Wake and Iron Leaves featured in this event can each be caught only once per save data. If you caught these Pokémon during a previous Tera Raid Battle event, you cannot catch them again. You can still participate in Tera Raid Battles against these Pokémon to obtain other rewards if you’ve already caught them.

The Walking Wake and Iron Leaves appearing during this event may be featured in future events or become obtainable through other methods.

Edited to add info from home. Thanks Flit.