What complexity tells us is that we can't predict with accuracy about complex systems. But not all aspects of a complex system are complex. Furthermore, there are things that influence complex systems. The key is feedback and shortening delays in workflow and in achieving feedback.
But Scrum makes many predictions:
The thing is, however, there is a model under Scrum, called Lean, that will help you see what improvements will be. See my next post for what we've been using for a long time and which you already know (intuitively anyway).