The consensus that it isn't the last pack because it looks to have a "Mountain" theme is rather shoehorned, IMO. Yes, JWE2 did a "Park Managers Collection" as it's last DLC, but that is their only game to have done so, and may have only resorted to such a theme because the most requested species weren't able to be given a general overarching one (like with PZ's 'Conservation Pack', for example). In comparison, Planet Coaster's last DLC was the Ghostbusters story-focused IP DLC, with their last non-IP DLC being a standard "Classic Rides" pack. JWE1's last DLC was an OG Jurassic Park story-focused IP DLC (adding content they supposedly had originally planned to be in the base game, but was pushed to DLC due to rushed development), with their last non-IP DLC being a standard "Herbivore Dinosaur Pack". It could well and truly be the case that a DLC with an overarching theme is Planet Zoo's last DLC, what matters is the features included in the DLC/update, and their communication during & after their respective releases. And though it doesn't mean as much as later communication, based solely on what they've released so far, I would hesitate to be sure of a DLC succeeding this one no matter the theme/name it ends up getting.