The remake of Halo CE will only include the same species as in the original. There has been no word on any future word on any other halo games, so its to early to speculate on new races/species.
The website of, I believe, 343 Industries on Halo 4 says that there is an "ancient evil." This could be either the Flood, the Forerunners, the Precursors, or something completely new.
i have a feeling there will be since its a new trilogy.
Path1k 23:48, July 7, 2011 (UTC)