A mix of 2 and 3. Its obvious it was meant to be the final pack I mean come on they have the Frontier HQ in the campaign for god sakes but I think they decided to keep going because they somehow knew ahead of time that Planet coaster 2 might not be the major sucess they thought it would be (and good predictions for them cause they were right) so to play it on the safe side basically as a "fail safe" have a remainder of the PZ team stay back and make another pack for next year because thats a guarantee to make them money.
- It was never intended to be the last pack, and truly meant to be a fifth anniversary DLC through and through. And the roster and theming was a "Thank you for five amazing years!" thing
- It was 100% meant to be the last pack as is - BUT in the last minute, whether it was a higher up, the devs, the King of Frontier, whoever, decided "nah, we gotta keep going" - fueled mostly by the success of the console release
- It was meant to be a final, larger pack a la Ghostbusters in PC or Jurassic Park in JWE1, but halfway through they decided, "f**k it, we'll just double our profits and split it in two". Zookeeper's will be the B-team, whereas the next pack will be the heavy hitters - think tree kangaroo, South American monkeys, walrus, you-know-who-with-feathers-but-I-don't-want-to-jinx-it
imo I think this is the most likely option
- Who cares we're getting more animals, BABY.
I say part of 3 because I think they would've wanted to make a large pack with all of the community favourites but couldn't afford the resources and time so they took a handful in one pack and saved the rest for whatever the fail safe pack is releasing this year. I don't think this next pack will be anything more than the zookeeper pack was. No higher price, no extra stuff, no birds, just business as normal.