Kingdom of the Planet of the Apes was the start of an all-new Planet of the Apes trilogy, meaning that these 10 classic franchise characters could appear in Kingdom of the Planet of the Apes 2. Kingdom of the Planet of the Apes carries on the story of the modern series while also bringing the Planet of the Apes lore closer to the original movies than ever before, setting up an exciting possibility for the future. Because of this, it’s been theorized that more classic characters could appear in Kingdom of the Planet of the Apes 2, like these 10.
https://screenrant.com/planet-of-the-apes-classic-characters-appear-kingdom-sequel/