This is according to a recent sighting in the Nintendo Switch eShop by Twitter user @LordofGamez in which as you can see in the screenshot below, it shows that the game has been listed as having a December release. There is no specific date mentioned, but it states that it has been planned for a release in December.
Is this news? if it is: pic.twitter.com/BDsINlwIyU
— log (@LordofGamez) November 7, 2017
This is in line with what we have previously heard, in which Nintendo themselves confirmed that the DLC is on track for a release by the end of the year. There were earlier rumors suggesting a 10th of November release, but based on this sighting it is clearly not true. As for specifics, Nintendo did promise that they will be sharing a date soon, but either way it looks like December is the timeframe that we are looking at.
The Legend of Zelda: Breath of the Wild Expansion Pass is available for purchase for $20 and is available on both the Nintendo Switch and Wii U. In addition to the expansions, the Expansion Pass will also contain new armor, treasure chests, and more.