Halo Infinite: Campaign co-op won't make it to Season 2 launch
Joseph Staten of 343 explains, "We still aim to release the co-op campaign later in Season Two, and we'll be sharing a release date as soon as we can. It takes longer to have a high-quality, comprehensive 4-player network co-op experience in the massive, open world of Halo Infinite."
This is related to online co-op, but it looks like the two-player split-screen co-op co-op will also arrive at the same time: "We're also committed to creating a great split-screen two-player co-op experience across all Xbox consoles, from the original Xbox One to Xbox Series X – the non-linear and open sections of the Campaign present great split-screen challenges, and more time is needed to solve them."
Regarding the Forge, however, for now there are no changes to the arrival scheduled for Season 3. We await new news on this.