We can safely state that rumors that a Watch Dogs Nintendo Switch 2 listing came up online was faked.

There was an earlier rumor that a Game-Key Card listing for a Watch Dogs Dedsec Collection came up on a Czech video game retailer website. But billbil-kun examined the evidence and concluded that the listing was fake.
For one, the faked listing did not have the Ubisoft logo on the case. Subsequently, the product code was also proven to be inauthentic.
To be clear, billbil-kun is not saying that he’s sure Ubisoft is not working on bringing the Watch Dogs games to the Switch 2. He verified this specific store listing on its own.
Ubisoft’s future is uncertain, much less their future plans on Nintendo’s platforms. While they had previously demonstrated extreme loyalty to Nintendo, they recently confirmed that Assassin’s Creed Black Flag Resynced was not coming to the Switch 2.
On the other hand, they are still bringing Rayman Legends Retold and Rayman Origins: Enhanced Edition to Nintendo’s platform. So we will just have to wait and see what Ubisoft announces in the future.
