Teacher Yoda
By the time of The Acolyte, Yoda had been Grandmaster of the Jedi Order—their eldest and most revered leader—for millennia. He would thus already be the most significant voice in the Jedi Council, the one whose view everyone around him sought after. Vernestra Rwoh looks most likely the Master of the Order, in charge of supervising the whole Order, so she would be closely collaborating with Master Yoda.
Showrunner Leslye Headland says Yoda won't be making an appearance in The Acolyte, although it might simply be a ruse. Whether he is or not, though, he is definitely being kept informed—albeit on an unauthorized basis. Notifying the Jedi Council worries Vernestra since they would have to provide reports to the Senate, hence exposing the Jedi to political opponents runs a risk.
Yank.
Though little is known of Yoda's enigmatic extraterrestrial species, he wasn't the only one of his race seated on the Council. Just 483 years old at the time of her death in the Tales of the Jedi series, Yaddle was younger than Yoda. Still, during The Acolyte she was an elderly, experienced Jedi Master. Like Yoda, Yaddle had long loved working with the Jedi Younglings and frequently travelled the galaxy with them.
Yaddle's emphasis on Younglings suggests that she collaborated closely with Master Sol, who has already been depicted imparting the foundations of meditation to Younglings. Said another way, she seems improbable to show up in The Acolyte just because she wouldn't be a go-to source when talking about unexplained Jedi deaths. Still, the potential cannot be discounted, and it would be fantastic to see more Yaddle.
Oppo Rancisis & Yar Elena Poof
Masters of Jediness Serving members of the High Council throughout Lucasfilm's Star Wars: The High Republic volumes, a century before The Acolyte, Oppo Rancisis and Yarael Poof are two of the oldest Star Wars characters. One could also reasonably presume they were sat on the Jedi Council during Mae's frenzy. Though their lifespans are unknown, Thisspians and Querians are obviously far longer than humans.
Other nonhuman Jedi will also show up in The Acolyte quite definitely. Known to live for far over a hundred years, Mirialans like Vernestra Rwoh may show up Luminara Unduli. At this point, too, the Cerean Ki-Adi-Mundi might be a Jedi Master. Even Pau'ans like the Gran Inquisitor might have long lives; he was a Temple Guard prior to Order 66, thus he could have readily surfaced. Ironically, because he would be sporting a golden Temple Guard mask, he would be more difficult to spot.
Jamba the Hutt
In the Star Wars galaxy, Hutts are verified to be an astonishingly longlived race. Born in 600 BBY, Jabba had already lived for millennia based on The Acolyte's chronology. That yet, he was hardly as strong and influential as the villain depicted in Return of the Jedi. Jabba would have been only one of many Hutt commanders; it's even likely he hadn't moved on Tatooine yet, instead functioning from Nal Hutta or the moon of Nar Shaddaa.
Actually, the moon of the smugglers was mentioned in the first Acolyte episode. Apparently Osha's fellow Mekneks visited there just before the episode, which suggests the kind of company Osha was maintaining. Still, that's most likely the closest The Acolyte will produce for a formal Jabba The Hutt Easter egg or appearance.
Chefbacca
Though Wookiees live longer than people, Chewbacca in A New Hope was 200 years old. Over his lifetime, Chewbacca would meet numerous Jedi; he ran across Ahsoka Tano during the Clone Wars and Yoda personally in Star Wars: Episode III - Revenge of the Sith. There is no actual justification for excluding the chance Chewie came across Jedi many more times.
Though his name ends the same, the Acolyte is verified to feature the Wookiee Jedi Kelnacca; he most likely has no relationship to Chewie. Wookiee naming customs are not well known, but Chewbacca's father was Attichicuk, hence the "bacca" component obviously isn't a family name. Though it can't truly be ruled out, that does make a Chewbacca cameo seem somewhat improbable for The Acolyte. The show might travel to Kashyyky, which might perhaps bring other Wookiees.
Mazkanata
The fascinating Force-sensitive figure Maz Kanata, who obviously had a past with the Jedi (and once referred to Master Yoda warmly as an old flirt), debuted in the Star Wars second trilogy. Star Wars: The High Republic progressively reveals from this past that there once was even a Jedi Temple on Takodana, the planet Maz has seized as her headquarters of operations. The pirate queen worked in harmony with the Jedi.
By the time The Acolyte arrives, that Jedi Temple has been gone for a century; however, there's no evidence Maz Kanata isn't still eager to collaborate with the Jedi. She is definitely a valuable contact in the criminal underworld, hence she might be helpful looking into Mae and the unidentified Sith Lord. Still, there isn't any proof Maz will turn up as yet.
Dexter Jetta
Hearing that even Obi-Wan Kenobi's informant had a centuries-spanning Star Wars past would most viewers find shocking. Star Wars: The High Republic reveals Dexter Jettster (or "Dex" for short) was a pirate roaming the High Republic Era, sporadically collaborating with Jedi. Apparently, besalisks live far longer than anyone would have guessed.
For millennia Dex stayed a part of the galactic underground, finally running upon Obi-Wan Kenobi in Kiersten White's Padawan. Obi-Wan was the one who persuaded Dex to give up his life of crime, hence he would still be engaged in swashbuckling acts of heroism during The Acolyte. This season most certainly wouldn't be suited for that, hence a cameo isn't really likely. Still, Leslye Headland has always hinted for The Acolyte season 2 thus he could still show later rather than sooner.
