Over 230 past-gen Pokemon will return to Scarlet and Violet via their DLC

gamesradar.com:

Several returning Pokemon Scarlet and Violet DLC creatures have just been revealed for launch later this year, with more yet unannounced.

Earlier today on February 27, a new Pokemon Presents showcase announced The Teal Mask and The Indigo Disc, all-new DLC instalments for Pokemon Scarlet and Violet. Now it's been revealed that each new DLC expansion will boast a metric tonne of returning creatures from past Pokemon games.

For the first DLC, called The Teal Mask, the likes of Milotic, Yanma, and Ninetails will all be debuting in Pokemon Scarlet and Violet. That's in addition to Shiftry, Chingling, and Vikavolt, all six of which are older creatures from the Pokemon series, returning for this new DLC instalment.

The second DLC expansion is called The Indigo Disc. Zebstrika, Dewgong, Metagross, Espurr, Alcremie, and finally Whimsicott are some of the returning creatures set to return with the second DLC. After the Pokemon Presents showcase wrapped up, it was revealed that over 230 returning Pokemon will be made available through both DLC expansions, but these are only the ones we know of so far. 

The Teal Mask will be arriving for Pokemon Scarlet and Violet in Fall 2023, while The Indigo Disc will be launching just a few months later in Winter 2023. 

More immediately though, Pokemon Scarlet and Violet are getting new Paradox Legendaries in the immediate future, in the form of Walking Wake and Iron Leaves. Both newcomers will be debuting in the two games very soon, once the new update for Scarlet and Violet is launched worldwide after maintenance. 

Check out our Pokemon Scarlet and Violet PokeDex guide for a complete look at all the creatures currently in the two games.