Judging by Halo Infinite artbook release date, the game could release sometime during Summer 2021. The artbook is scheduled to arrive in June, suggesting that the game's release could follow closely.
Xbox's biggest franchise Halo has seen many ups and downs since 343 Industries took over the development from Bungie. The upcoming game, Halo Infinite, has already been delayed even though it was planned to be a launch title for Microsoft's next-generation console Xbox Series X.
Shortly after the gameplay reveal at Xbox Games Showcase, Microsoft confirmed that the game has been delayed into 2021, which was a massive disappointment to many Halo fans, but also a decision that the community accepted.
Xbox did not specify the new release date but the game should come in mid-2021 and the latest listing of Halo Infinite artbook suggests exactly that. The Art of Halo Infinite - by 343 Industries, book, which you can find on Target's store, is set to arrive on June 29, 2021.
This could mean that Halo Infinite game release could follow shortly after that. It's also possible that the game releases before the artbook. Some Halo fans probably expected to see the game early in 2021 but Summer release date or even late 2021 was always a more realistic scenario, once Microsoft decided to move the release from Xbox Series X launch.
All in all, we suggest you take this as speculation since, at this moment, it's nothing more than that. For more solid info, stick to 343 Industries and Xbox social media channels, who are likely to talk more about Halo Infinite in the upcoming months.