How's your vault holding up? Chances are you've neglected your duties as Overseer, leading to a vault filled with starved dwellers and radroach infestations. Five years is a long time to be responsible for the well-being of a whole community!
There's a good chance you'll get a fresh start. According to Pocket Gamer, Bethesda is gearing up to release Fallout Shelter Online on both iOS and Android. This isn't a sequel so much as an expanded version of the original. More specifically, it's a localized take on the game that launched in China in 2017.
Fallout Shelter Online has a more fleshed-out campaign that takes your character outside the vault to search for the original Overseer. This venture leads to all sorts of familiar Fallout locations like Fenway Park repurposed as the settlement of Diamond City. There's also an online battling component.
However, the most marked departure in the Chinese version is a gacha component, which is a hero-collecting system where you build teams of companions to accompany you. Like most every gacha, it's hinged on rarity. Nick Valentine is given as an example of an extremely rare (and desirable) hero to collect.
On one hand, it's a more robust version of Fallout Shelter that aims to tell a more complete story. On the other, it's probably going to be a microtransaction wasteland. Fallout Shelter Online is expected to launch in late April. Then you can figure out if this vault's worth saving.