In a very, very rare feet, Bungie actually gave away some story explanations for a Halo game prior to that game's launch. In this particular instance, it came via their Weekly Update and consisted of a detailed explanation as to why gamers will not fight a single Elite in Halo 3: ODST.
If you haven't played through Halo 2 and intend to, you'll want to stop reading right here as the below contains spoilers.
Taken straight from the source:
"We realize that the Elites are of a fan-favorite, so it's probably wise to set aside your compassion and steel yourself for what is about to come. There are no Elites to fight in Halo 3: ODST.
Still here? Good. Deep breaths. We wanted to clue you in early so you didn't have a chance to let your expectations wind you into a whipping maelstrom of assumption and conjecture.
In the wake of Regret's shameful retreat from New Mombasa, the Prophet of Truth continued his maneuvering - one eye always on his ultimate goal: his rightful and holy ascension. For Truth, his own personal passage was paramount. His Godhood would not be denied. Everything else was secondary.
And though Truth's duplicitous scheming doesn't come to full fruition until the Elite Honor Guard's failure to protect the Prophet of Regret affords him with the final leverage needed to appoint the Brutes to the lofty position, his plans were never made in haste. They were well laid. When the time came to return his attention to Earth, his expendable regiments needed to be led by Jiralhanae, not Sangheili.
Leaving the Elites to scour Earth in search of a Holy Forerunner relic, and ultimately to uncover the most precious and sacrosanct Forerunner artifact in existence - the very portal that opened upon the Ark itself - would have placed all Truth's aspirations upon the shoulders of a species he had already decided to cast aside, a species splintered by heresy and derision, even amongst their own ranks.
Truth's divisive mandate had been set in motion. The Elites had exhausted their usefulness to him, they would not be allowed to meddle in his affairs any longer, and he would not place his rightful transcendence into the hands of incompetents. His word was law.
So the Prophet of Truth deploys Brutes. And the Brutes were eager to prove that their loyalty and battle prowess had earned them a seat at the side of the Hierarchs, as the honored protectors of the sacred Covenant. Such blind faith and eagerness marked them as near perfect pawns for Truth to sacrifice."
This has me very, very disappointed.
Elites were very well developed in Halo 2 and were key to the game's story, yet that very plot line was all but abandoned in Halo 3, where Elites became a rare site save for the Arbiter, who was demoted to the rank of sidekick. I thought surely that Elites would not be neglected in Halo 3: ODST since the game takes place during the very time as we last saw them shine, but Bungie's shafting them yet again.
So the only place we'll continue to see the noble and zealous Sangheili, aside from going back to the original Xbox, is in Multiplayer. Except instead of hearing an Elite shout at me "A thousand curses Demon!," it's some annoying kid shouting a thousand curses at me through his Headset, at which he gets muted and reported via the lovely Xbox LIVE Complaint system. Somehow, it just doesn't amount to the same experience.
At least we'll have Elites to fight and control in Halo Wars, but even that's not the same thing.