If I'm recalling right, we've gotten 4 primates out of 17 packs (and one anniversary Lemur). As much as the game needs more primates and they would be deserving of this kind of pack, it's almost certainly not going to happen.
ETA; 3 of those 4 have been from Asia as well, Africa and South America, both also well known for primates, combined have received a grand total of one monkey and one lemur in 56 months.
Most essential primates right now are:
Another Baboon {Really needed right now especially Gelada/Hamadryas, but Olive wont hurt either}
Spider Monkey {Brings a beloved primate with unique animations}
Howler Monkey {Brings a unique and vocal monkey to the game}
Mantled Guereza {An amazing monkey for African Exhibits}
De Brazza {Some of the most known Primates from Africa}
South American Monkeys & African Monkeys in General
Somewhat Essential Primates:
Squirrel Monkeys {A small and good monkey for Educational areas}
Golden Snub Nosed Monkey {For Chinese and Asian Exhibits}
Lion Tailed Macaque {Amazing Indian Primates that are quite iconic}
Langurs {General monkey that can be seen in zoo's all over the world}
Coquerel's Sifaka {Adds more for Madagascar habitats}
Aye-Aye {Amazing and would add a good nocturnal primate to Nocturnal houses}