In essence, what this vision provides you is knowledge that each of us has already had: that, like all men, you are mortal, and will someday die. Hominem te esse memento, memento mori, and all that.

That we will all someday die is inevitable; this vision is but one potential version of that death. And as multiple elements of Miss Perks' vision are clearly counterfactual — I was not teaching at Hogwarts when the children were younger; Sanji Patil is dead and cannot be Sorted — it is impossible to tell which of the remaining are true visions, and which are phantasts.

The potion is no longer in favour for that very reason. Do not allow yourselves to dwell upon what might be or what might never come to pass.