Foreshadowing is a something that indicates a future event or shows symbolic meaning. Some people on the base don't use foreshadowing in their reasons. Such as (Sorry Sakura haters...) the whole summoning scene in the war represents that they are on the path to earning the sannin name. So sakura during the war isn't going to die. Also how naruto and sasuke have gotten stronger throughout the series means fate will have them collide in a battle(one on one). It's a common thing to use in a story. And with the first hokage being the one to defeat madara who ended up surviving set the stages to what is happening now. Madara has caused this whole mess and it will end after naruto (the savior) achieves peace.