Reports state that the development of Halo Infinite actually got help from outside game developer 343 Industries.
Gears of War studio The Coalition has actually provided assistance to 343 Industries in making some progress in the development of the upcoming sequel. Twitter user @bogorad222 shared a screenshot that featured former Coalition Level Artist Adam Bodden with his LinkedIn post about his work on the game. He mentions modeling proxy meshes, setting up assets request sheets for the environment art team, and more.
Another former Coalition staff, VFX Artist Hugo Gutierrez Mares also mentioned that he has worked on the campaign and cinematics for the game.
These are just some of the assistances 343 Industries got from the outside but who knows there could be more. At least this could make their progress move forward than getting delayed even further.
Halo Infinite was supposed to launch last year, but when the game demo was previewed, there was some bad feedback. The staff felt they wanted to improve it further, which is why it was delayed to this year.
Halo Infinite will launch on PC, Xbox One and Xbox Series X/S later this Fall 2021.