If a three-dimensional object passes through a two-dimensional world, only a single layer with width and height becomes visible in that world. The third dimension, depth, becomes lost when a three dimensional object enters a two dimensional world. This is demonstrated here: https://www.youtube.com/watch?v=BXngATAQ0m0
Now it is ridiculous to say that because some 'layers' have not yet become visible in that two-dimensional world as the object passes through, these layers therefore do not exist.
If we apply this simple occurence of truth and simply add a dimension, we reach the conclusion in analysing our own existential realm aka the "World" that we are three-dimensional beings passing through, or rather being past through a fourth-dimensional object called "universe" at the pace of one second per second. We live within this object and off of this object, of course.
Applying the logic now of the yet unseen "layers" already existing, it can be concluded that indeed, the future already exists and is pre-determined since the universe's creation.