Sometimes, people are just absolutely sure about how events will play out. In their eyes, it's already a Foregone Conclusion. They're so sure, in fact, that they feel the need to stress how it's not a matter of if things will turn out like they believe. It's a matter of when.

Note that this trope requires putting particular emphasis on using when and not if; a statement that casually assumes a future event will happen doesn't count. Also, this trope doesn't necessarily require the statement to end up being right. In fact, examples of this are often followed by