I would presume you talk about Lord Hood. Or Rtas Vadam?
Either Or. Lord Hood comes and goes to talk peace with the sangheili. However half the sangheili population disagree that humans are worthy to keep their truce fire. So the ones that disagree with humans plan to go out and eliminate them.
While ONI has the same motive. To go out and exterminate the sangheili behind Lord Hood's back.
Rtas Vadam, isn't talked about alot. So I presume he's along side the Arbiter, as they are both from the Vadam keep.
I'm doubtful, but than again it's 343. I heard a rumor that they may bring back Cortana (Which I find a poor excuse) As she sacrificed herself, and her life expectancy was over 8 years. That and she corrupted her core.
However, I'll be curious to see 5. I was more hoping a different storyline.
Perhaps..reflecting on a forerunner (unnamed) and the forerunner-flood war. Or the forerunner-precursor war. Hell even the ancient human-forerunner war.
Or an opposing storyline such as. The flood's point of view. Covenant point of view. Storm covenant point of view. Jul madma's point of view. ONI's point of view. etc: