While discussing the Xbox Game Pass, the post-apocalyptic series was mentioned. While nothing has been confirmed by Bethesda, having Fallout mentioned alongside other confirmed upcoming titles certainly leads to speculation.
In a recent interview with GamesRadar+, Ben Decker , Xbox's Head of Services, was discussing games joining Game Pass on release, specifically mentioning Forza, Halo, and Fallout.
Halo and Forza are confirmed to be working on, so not a surprise, but Fallout's appearance essentially confirms that a new title in the series is on the way.
This statement not only shows the new Fallout game, and a new IP that hasn't been disclosed, but also that Xbox is committed to getting titles onto Game Pass as soon as possible. Even without a new Fallout, it seems like Game Pass is gaining more and more benefits.
With E3 on the horizon, we will hopefully soon see something official about this new Fallout and the new IP.