It makes sense that he would get an upgraded look, especially with what what 343’s Jeff Easterling said earlier this year during another Mixer live broadcast to discuss the future title. "It is Halo 6," he forcefully iterated. “You should just consider it Halo 6. Don’t think of it as a weird prequel kind of thing. It’s the next story. It’s the next chapter in what is going on.”
https://comicbook.com/gaming/2018/12/15/halo-infinite-master-chief-first-look/