A number of people have pointed out a pair of provocative items in the PCGamer Halo preview, which state that Halo is around fifty percent complete and is due out in the Fall.
Hate to be the bearer of bad news, but don't count on it. While the fifty percent part might be accurate, Fall '99 is too early for Halo, and Fall '00 is three to six months after Bungie's proposed release date. Just remember: don't place too much weight on release dates, or you're likely to be disappointed.