According to this Wiktionary page,
A small number of English adjectives take noun phrase complements. CGEL lists only four: due, like, unlike, and worth. Underweight and probably overweight are also in this class. There may be others.
So, "a major cyber attack.." is a complement that the adjective due takes in your sentence.
The meaning, again according to Wiktionary's entry on due, is "owed or owing". Wiktionary provides the following example:
He is due [four weeks of back pay]. (a noun phrase complement in square brackets)
The note "not before a noun" means that due in this sense cannot be used as an attributive adjective, but only as a predicative or postpositive adjective. An attributive adjective is used like this:
The threat of cyber attack should be given due attention. (the adjective due stands before a noun, and this noun is attention)
In your example sentence, due is used predicatively. It would be hard to use it attributively in this sense anyway, since we need to attach the complement to it somehow:
The experts say that our world is a due [a major cyber attack causing widespread harm before 2025] world.
(I used due before the noun world, that is, attributively, and inserted the complement between the adjective and the noun. The result looks outlandish).
Best Answer
Statistically, and cross-linguistically, at university is more commonly-used than in university. Here's some numbers:
I wouldn't call any of these an overwhelming majority, so what's the difference?
Here's a clear case where you can't use at:
So, for the meaning of in that corresponds roughly to in the course of, you can't use at.