BioWare doesn't have plans for Dragon Age: The Veilguard DLC right now, but that's mainly because the team is focused on ensuring the game ships with a complete story that isn't begging for a follow-up ending, as was the case with Dragon Age: Inquisition.
When asked about possible future additions in an interview with YouTuber MrMattyPlays, game director Corrine Busche explains that she's a "huge fan" of Dragon Age: Inquisition's Trespasser expansion, which wrapped the entire story with a nice bow and served as a bridge to the inevitable sequel. But Busche also says that Trespasser was "so essential to the Dragon Age: Inquisition story, it arguably should have been part of the base game."
