Given the open banner space and the OCD-triggering placement of the banners within the embassies. We’re likely to get one last pair of allied races to smooth things out. With the reveal of no 8.3.5 we’ll likely get this last pair in the prepatch.
So far, the trend in allied races has been to closely meet the class selection of the original race while keeping in mind story and cultural elements.
Alliance:
3M Pala 2AR Pala
5 Rogue, 4AR Rogue
2 M Sham, 2AR Sham
6 M Mage. 5AR Mage
4M Warlock, 3AR Warlock
5M Monk, 4AR Monk
2 M Druid, 1AR Druid
Horde:
2M Pala, 1AR Pala
5M Rogue, 4AR rogue
4M Shaman, 4AR Shaman
5M Mage, 4AR Mage
5M Warlock, 2AR Warlock
5M Monk, 5AR Monk
2M Druid, 2AR Druid
Given this information, the last allied race pair needs to be a paladin, druid, mage, warlock, rogue for the alliance. The Horde meanwhile needs a paladin, warlock and rogue.
Given this information, along with allied races needing an associated reputation aides in narrowing down candidates.
Alliance:
Ankoan: Would have shamans as a bonus class. They’d likely exclude priests as Ankoan seem far more shamanistic than priestly (they don’t seem to grovel in prayer). Warlocks are a bit iffy, but a burial shrine also shows that Ankoan aren’t above deception and unhonorable acts. Paladins are easy enough to imagine, given their emphasis on martial prowess and rigid code of honor. Druids are also likely given their naturalistic and nomadic lifestyle.
Sethrak: Far less likely on account of no reputation and the only interaction being a short quest-chain. They’d either have shaman as a class, or exclude them. I don’t recall the Sethrak doing any shamanistic practices that weren’t subjugating the elements. Paladins and druids can be explained through the Zandalari method.
Beyond these two it’s a wildcard. They could do some weird tol’vir worgen thing with the Uldum accord. But why?
Horde:
Rajani Mogu: The most likely choice given their reputation, leaderless state and not-enslaving of other people. They could have paladins, seeking out the order and structure that the holy light provides. Mogu also practice dark, warlock-like magic. As titan-forged they have a natural affinity for the arcane, and Mogu are not above deception and sneaking about. Monk is unlikely simply due to the sheer history, and the Shado-Pan probably hunting down the Huojin just for thinking it. Shaman is also possible, although Mogu lean more towards subjugation than bargaining.
Sethrak: A little more likely than the Alliance side, but they lack a reputation with the Vulpera absorbing the Voldunai rep.
Glowing Undead: Unlikely. While they fit paladin, they likely couldn’t be warlocks. Rogue is also a bit unlikely. There’s also no rep or lore associated with them.
The last pair in my opinion would be Ankoan and Mogu. Which provides a good Pandaria thematic. Ankoan recruitment could involve them meeting a renewed Pearlfin, learning more about the Alliance that aided them in their quest to slay Azshara and convince the other Ankoan clans to aide the Alliance.
The Rajani recruitment could focus on the mogu struggling to deal with the loss of Ra-den, dealing with an upstart trying to pull a Lei-shen. Learning how to deal with their loss with the Forsaken who have also suffered similarly. Before swearing to aide the Horde.

