The possibility that The Legend of Zelda: Tears of the Kingdom may have DLC or story expansions is a very real possibility that will most likely not surprise anyone as the previous game had many of them, but this is the first official mention of such a possibility on the game's official website published by Nintendo.
Under the headline "Full game required to use DLC sold separately" on the official website The Legend of Zelda: Tears of the Kingdom (in English)
It's also interesting to note that this double asterisk does not even have any more precise ones. Either way, It's possible that The Legend of Zelda: Tears of the Kingdom has DLC, given that The Legend of Zelda: Breath of the Wild has them.
Although it is unclear whether or not this definition refers to cosmetic content or amiibo in-game goods (already confirmed) or actual add-ons, it's likely to mean both, with the most significant changes likely to follow a few months after the game's release.