I imagine Microsoft won't allow it, but honestly, a delay might be good. Hell, they could release the free to pay multiplayer this holiday, then save the actual Halo Infinite package for next year when it's fully ready. Shipping out a paid game that isn't content complete doesn't feel great, especially since Halo is beloved for having so many modes and options.
I understand that Microsoft needs their AAA exclusive, and I get that not having one yet for their new console isn't a great look, but this is maybe the most important game they've released in over a decade. They need to get it right