I’ve only ever used that phrase as a joke. I.E. when somebody agrees with my opinion on something I might say their opinion is “correct” despite it being, well, subjective. The only other time I use it is if somebody states a fact with “in my opinion” e.g. “in my opinion, the net energy of an isolated system never decreases.”
I’m not sure what the context you saw it in was, but I suspect they were making a joke because having a “correct opinion” is, indeed, impossible.
If I say, about a particular piece of proposed legislation, “In my opinion, this is a bad law. It would have disastrous effects on the nation.” (And maybe I’d go into more detail about what disastrous effects I had in mind.) That’s the sort of opinion about which I might well be correct, or incorrect.
“It’s bad” is an opinion, and can’t be correct or incorrect (somebody may think ill effects are good). “It will have disastrous effects” is a statement of fact that can be true or false (or be unknowable). Well, okay, the word “disastrous” is a bit of a connotative word, but the general implication that the action will cause an outcome contrary to its intent is factual at least.
There’s an entire class of Temporal Logics which deal with things like “until” or “in the future”. In fact, it’s the source of one of the more infamous and troublesome logical conundrums known as the Yale Shooting Problem. But in general, we can even use it in propositional logic, the problem is you need a separate atom for every state of every object at every point in time.
The problem with real life is more that the statement “X will be true in Y <units of time> if Z happens” is a bit of a pain to evaluate in a formal manner given the complexity of real life.
