I would call it realism if there were any evidence of such "situation". Absolutely nothing indicate that the support is ending and if you believe it is just because they did not announce new update EXACTLY after 3 months since last dlc then it IS a pessimism.
1) There's been absolute silence from PZ regarding future dlc (ex: no mention of future themes or animals have been announced AND Steamdb went silent)
2) There have been persistent rumors that Planet Zoo IS ending support very soon lol
3) Also, like you pointed out it has been 3 months since the last dlc...and still no teaser, no announcements, and no leaks literally no word about a new dlc.
So is that pessimistic to take into account all of that information and then make a decision based on it?
You are very confident there will be Fall dlc.
Can I ask what is your proof? There are a lot of North American species still missing in PZ. But that's not proof of Fall dlc. I could have said that in November 2019.