By 2020 there will be two official Fallout RPGs, and both are by Modiphius.
Modiphius already holds the license from Bethesda Softworks for the Fallout: Wasteland Warfare wargame which offers both squad v squad battles as well as narrative campaigns. The first of the new Fallout RPGs will be an expansion of that game.
The Fallout: Wasteland Warfare RPG is being developed by James Sheahan, the miniatures game developer, and will let players create characters, explore the world, interact with familiar Fallout NPCs, have guidance on building settlements and learn about locations. It’s due as soon as the summer of this year. However, you need to have the Two Player starter kit for the wargame to play the RPG.
A second RPG, one which uses the 2d20 system Modiphius uses for games like Mutant Chronicles, Conan and Star Trek Adventures, will be completely standalone. This traditional RPG is promised for 2020.
Modiphius have more information on the games available from their website and a newsletter sign up.