Halo Infinite has no fixed release just yet, 343 Industries community director Brian Jarrard has confirmed.
In a PSA tweet, Jarrad says 343 Industries "haven't locked on [a] release date for Halo Infinite yet", adding that any listings you see on retail sites with an exact release date are just placeholders or speculation.
Halo Infinite was originally set to be the big Xbox Series X launch title coming in Holiday 2020. Now that we know the next-gen console's release date, that would have put the initial launch of the new Halo title at November 10, but 343 Industries announced back in August that it would be delaying the release. In the statement from the studio, it gave a 2021 release window, and it looks like we won't be getting an exact date just yet.
PSA: We haven’t locked on release date for Halo Infinite yet. Anything you see on a retail site is just placeholder / speculation.September 24, 2020
Studio head Chris Lee said the decision to delay the release was a "result of multiple factors that have contributed to development challenges, including the ongoing COVID-related impacts", and added that it was not sustainable for the well-being of the team and the overall success of the game to ship it this holiday.
Just recently an anonymous developer who goes by Qilin at 343 Industries posted an update about Halo Infinite on Twitter, confirming that new features have been added to the game as a result of the delay. Interestingly, Qilin also said that "it won't be too long before Halo Infinite's release". For the time being, though, we'll have to wait for an official release date to find out when in 2021 we can expect the return of Master Chief.