https://wccftech.com/halo-infinite-campaign-co-op-may-2022-earliest/

Halo Infinite campaign co-op and Forge mode have been pushed back from their announced release window, 343 Industries confirmed.

Speaking with Eurogamer, 343 Industries' Joseph Staten confirmed that the extension of Season 1 to May 2022 ended up pushing back the release of campaign co-op, which was scheduled to launch in Season 2. This is still the target, according to Staten, but things can change and they are not ready to commit to any date at the time.