Josh Sawyer, the director and lead designer behind Fallout: New Vegas has said they would be open to returning to the post-apocalyptic series. Developed by Obsidian Entertainment, and published by Bethesda, the 2010 release is considered by many to be the superior Fallout entry, with its rich world building and impressive storytelling. Not that there's anything wrong with the other games in the franchise, but there's something about this particular entry that made it shine.
As a result of such popularity and critical acclaim, fans have been hoping for a Fallout New Vegas 2 for quite some time. However, Bethesda, as well as bringing the world Fallout 3 in 2008, took the reins once more for the fourth game and the less well received Fallout 76. On top of that, Obsidian has been busy developing other titles, such as The Outer Worlds, South Park: The Stick of Truth, and the newly released Pentiment. This means there likely won't be a sequel to New Vegas any time soon, but that doesn't mean it's off the table entirely.
In a recent interview over on the Kinda Funny Games YouTube channel, Sawyer has said they would be interested in returning to Fallout, saying they love the games. This could suggest they may one day return to do a new Fallout New Vegas entry. While this does not mean a new release in the series is on the cards, the director and designer did say they could see themselves working on it again at some point, adding "we'll see where the future takes me." When asked during the interview about a potential setting Sawyer would like to see, the developer said they hadn't thought a lot of about it, but did say places like California or the Midwest would be intriguing settings. The discussion begins at the 59:30 mark.
As mentioned above, Obsidian Entertainment recently launched Pentiment, an adventure game set in the 16th century which follows the story of Andreas, an apprentice working at the local abbey producing manuscripts. It's quite a departure from the likes of New Vegas, but it leans into the studio's strengths, that of fantastic storytelling and writing.
As for the open-world RPG series itself, it's known that Fallout 5 is in development, but it's likely years from completion. Given that this entry will be coming after The Elder Scrolls 6, with no indication on when that game will be coming out, fans are probably going to have to wait a long time until a new Fallout game. By that time, maybe Sawyer and Obsidian could do one to fill the gap.
Fallout: New Vegas is available now for PC, PS3, and Xbox 360.