Dontnod's vampire RPG Vampyr just recently hit a milestone of one million units sold and with that announcement a new game was teased with Focus Home Interactive, the publisher of 2018's Vampyr. The game, which has not officially been announced, was shown in a picture on Twitter taken during a reveal event and all we know so far it the fact that Dontnod is developing it.
Based on the aforementioned picture, it seems to be based on Norse or perhaps Celtic mythology, but we'll know for sure when we get an official announcement from Dontnod or Focus Home Interactive sometime in the future.