In an interview with Nintendo Everything, Game Director Genki Yokota has revealed that Fire Emblem: Three Houses' DLC might include new characters, but will not impact the main story.
Fire Emblem: Three Houses is the latest installment in the Fire Emblem series, an RPG strategy series that has been around for decades. This latest title, however, has made some significant changes to the formula. Players take on the role of a mentor at one of three houses of their choosing, teaching students who will eventually become their soldiers. A deep and meaningful story begins to unwind, with significant player input each step of the way.
The announcement that DLC content that will not impact the main story is both a blessing and a curse. Players who don't want to purchase the DLC won't be missing out on any additional plot points, meaning they get a complete narrative with the base game alone. With the growth of micro-transactions, along with more and more companies launching incomplete titles, it's great to see Nintendo going this route. On the other hand, the story told in Fire Emblem: Three Houses is so strong, it would be great to see it continue to unfold.
That being said, Yokota states in the interview that the DLC will be in the vein of a "spin-off," hopefully meaning that some auxiliary characters in the game will become more fleshed out. Yokota goes on to tell players that they may have to wait awhile for the DLC, as it will be, "...something very big."
The addition of new characters is an interesting prospect, and one that could lead to some wild speculation. If it is going to be "something very big," while at the same time not impact the main story, this could indicate the addition of an entirely new suite of characters, both friends and foes.
Although it was only released a few days ago, Fire Emblem: Three Houses already has some DLC content available. It's a minor addition, but players who download this DLC can change the outfit of the main character. There will also be some free DLC coming sometime in the near future, in the form of a new difficulty mode; Lunatic.