Todd Howard today upon being asked if the Fallout IP would be handed off (since it's Starfield next, THEN Elder Scrolls VI, and THEN maybe a new Fallout):

"Fallout is really part of our DNA here. We've worked with other people, and I can't really say what's going to happen, but we have a 'one pager' on Fallout 5...what we wanna do with it."