There is this rule for adjective order in English, and mostly, authors agree on it. These are the two resources that I found online that tell us about this rule(there are others).
https://www.thesaurus.com/e/grammar/adjective-order/
https://dictionary.cambridge.org/grammar/british-grammar/adjectives-order
If we want to be grammatically correct, which is the better option?
"possible future event"
or
"future possible event"
I think the former is the correct one. Because then we can ask "Is the future event possible?". Then again we can also ask "Is the possible event in the future?". I would like to know your thoughts on this.