Hoyoverse appears to be very busy recently, what with a new Genshin Impact game on the way, on top of a recently announced Honkai spin-off, and many other projects to keep an eye on.
It appears that two new accounts have surfaced with the names 原神：千星奇域 and 原神：千星沙箱. These translate to Genshin Impact: Thousand Stars Wonderland and Genshin Impact: Thousand Stars Sandbox, though some sources report it as Thousand Planets instead of stars. It seems that the terms 'star' and 'planet' are interchangeable for now. I found this through Seele Leaks, a trusted leaker in the Hoyoverse community.
While there's literally no confirmed information or anything other than the names, we can speculate a little. There was a rumor a while ago that Genshin Impact would implement UGC (user-generated content) in a new module. The original source for this news has since disappeared, but you can find a repost here.
There hasn't been any update since this, but we do know Hoyoverse consistently hires for new projects, including the new Honkai game that got teased during the Star Rail concert. It features characters from Honkai Impact 3rd and Honkai Star Rail, bringing together two worlds. Whether this new Genshin game does the same thing remains to be seen.
It could be that this leads on to Chapter 2, after the Travelers finish up in Snezhnaya and Celestia. After all, the Teyvat Chapter Storyline trailer hints that there's more to come after we finish up in the seven (ish) regions of Teyvat.
This could also be a sort of add-on or side project to Genshin itself. I sure wouldn't say no to a game focused entirely on Serenitea Pot building, or visiting more characters' homesteads to learn about the lore hidden in the game. We'll have to wait and see what Hoyoverse is currently cooking up.
As you sit and speculate, we recommend you check out the latest Genshin Impact update, which looks to hold a lot of lore, and new characters you can pull using Genshin Impact codes for primogems.