No, he won’t be unmasked, and yes, that is for the best.
One of the issues with how Master Chief has been handled of late is that he has been reduced from being an abstraction, a symbol that anyone can identify with and project themselves on to, to a person with a well defined backstory- which takes away the enigma and mystery that made him so alluring in the first place.
That said, there has definitely been a different kind of mystery associated with it all- fans do want to see their hero unmasked; the thrill of it is sort of like what Metroid fans feel when they consider Samus without her Varia suit, no doubt. Whereas the games have teased and implied an unmasking of Master Chief multiple times, it has never happened- and that will not change with Halo 5: Guardians either.
“I actually don’t even know if I can talk about that,” Halo 5 creative director Tim Longo said, as reported by Gamerant. “He doesn’t take his helmet off.”
I am personally okay with this- to use the Metroid analogy again, filling in the blanks of a character who is so popular because of their enigmatic and cryptic past in the first place never goes down too well- just ask the people who played Metroid: Other M.
Halo 5: Guardians will launch exclusively on the Xbox One this October.