Orc and Draenei Demon Hunters are the top candidates for the next Demon Hunter races if blizzard ever decided to add more races to the class. Many players want to see non-elf options added to the demon hunter class to expand variety to demon hunters. However, some players feel that it would not make much sense to add additional races to becoming a demon hunter that is non-elf or keep the existing races as-is. I will say to those players that it does make sense to add Orc and Draenei demon hunters, and it would not make sense to add Void elf or Nightborne demon hunters or limit the classes customization options.
Backstory:
The Illidari has returned to Outland and taken over the Black Temple and Hellfire Citadel to use as a base of operations to strike against minor Legion incursions in the Twisting Nether. With Akama (or shade of Akama) part of the Illidari, the broken have once again re-joined to further the primary objective of eliminating powerful demons. Recognizing that there will always be a powerful demon lord and the possibility that the Burning Legion could return, the Illidari have not remained idle after Sargeras's defeat. By establishing a presence on Outland once again and taking over Hellfire Citadel, the Illidari also has command over the Fel Horde to use as foot soldiers against demons. With Illidari leadership recognizing the need to train new elite demon hunters, they begin looking for possible candidates to undergo the process of becoming a demon hunter. Due to Blood Elves and Night Elves being hard to find in Outland, the Illidari must consider training non-elf races for the process. The Illidari requests that the Broken Draenei and Fel Orcs send their strongest warrior to undergo the ritual of becoming a Demon Hunter. During the training, they see that the Broken Warrior, during the process, begins to reverse the de-evolution and once again takes the form of an Eredar while adapting to the newfound power. The Fel Orc, throughout the process, begins to regain some sanity as a new presence of a demon is there to fight against. Both of these two new Demon Hunters are assigned a dangerous mission to eliminate a Pit Lord who has made a home in Outland and is rallying scattered Legion forces. The mission is considered a suicide mission, but it is necessary to measure these two new hunters' power. They succeed flawlessly and kill the pit lord and its forces and prove that Broken Draenei and Fel Orcs are worthy of being trained in the ways of a demon hunter. The Illidari requests that the Broken Forces and Fel Orcs send their strongest warriors to undergo the process of becoming a Demon Hunter.
Starting Experience:
Similar to Allied Race Death Knights there will not be a unique starting experience but a quick Cinematic and receive orders from Illidari Leadership to go to Azeroth and eliminate Demon Presence found there. This will start at the top of the Black Temple and portals to major cities will be available for quest completion. Orc and Draenei DH will start at level 10 and receive a pair of Warglaives and sent to the capital city to begin the leveling experience.
Challenges:
The challenges for Orc and Draenei demon hunters to become reality would be the creation of Unique Meta model, adding animations to the Orc and Draenei skeleton to make the class work, and the adding new skins/customization options. Besides that the other issue would be the right timing which most likely will not come anytime soon because another Demon Centered Xpac wont come for awhile.
Thoughts:
I believe the Illidari will return as an important faction once again in-game. It is feasible that with the Legion command wiped out, the lesser Demon lords will fight for dominance of the shattered Burning Legion. I do not believe that after the Legion Expansion, the Illidari's work is done. They can either become an organization that will work to slay powerful demons throughout the nether or work to destroy other troublesome forces in the Universe. Like how Allied Races became Death Knights in Shadowlands, there will most likely be a time where the forces of Disorder rally again to bring the Universe's destruction. I also believe Sargeras will come back somehow, as he was the Big Bad of the Warcraft Universe, and he was not killed at the end of Legion for a reason. (And Blizzard loves to reuse old villains)
Additionally, an Orc Demon Hunter was added to a Hearthstone Adventure. https://hearthstone.gamepedia.com/Karnuk,_Demon_Hunter