Board Thread:General Discussion/@comment-27086331-20151017060059/@comment-25090680-20151019015710

I'm pretty sure Otacon confirmed in game that he had about 6 months to live iirc, could be a year but no more than that. I doubt they'd bring him back in a sequel in any way. They have the oppurtunity to do what they want, use any existing character or make a brand new 1.

Even if they did decide to reuse him, unless they retconned his accelerated aging, he'd still be an old man. Even in MGS science there's been nothing to indicate they can reverse aging.