Rumour: 343 developing another title besides Halo Infinite
With the massive studio being dedicated to Halo, we assume its something related to the franchise.
343 Industries is probably one of the hottest developers right now after delivering a surprise beta of the Halo Infinite multiplayer, and judging from recent previews is also on track to bring back the Halo series to it's former glory.
According to the fairly famous Windows Central editor and insider Jez Corden, this isn't the only project this massive studio (at least 557 employees on LinkedIn) is working on. It was in the latest episode of the Xbox Two podcast, he said they currently have a second game brewing as well, without adding anything more.
As this is a dedicated Halo studio (even the name refers to Halo), we assume it is Halo related. 343 Industries has previously said that they are not making a new Halo Wars title, but we still assume it's probably something different not to take players away from Halo Infinite and compete with themselves.