Naruto is meant to be called the "savior of the world", which is a much more noble title than hokage. Furthermore we already know he is stronger that any of the actual kages. So getting the title now would really not be anything special. Furthermore Gaara and A both have already titles above kage as they are leader and army commandor of the 5 villages. So the title of hokage is really not a big deal anymore. I see it as the dream of Naruto as a child. The page is turned now and we're up for much more than that.
Tsunade dying (if she does) doesn't have to be now either. One of the villains will get much stonger than actual Tobi, Madara, Kabuto, Sasuke. Levels goes on increasing since episode 1, and I believe it won't stop. Think about the finding in Oro's cave which is supposed to be that powerful that the user will win the war. I like the idea written today about edo-ing the whole Ushiha clan. All you need for that is the DNA which is in the jars of Tobi. So Tsunade could also die at the end of the serie, killed by the final villain with powers equal or superior to the so6p.