Okay so to start, the story of Naruto is essentially the story of two friends, rivals, and “brothers” (Naruto and Sasuke). As their relationship develops it is ultimately revealed that they are reincarnations of the sons of the Sage of Six Paths (Indra and Asura). Indra being Sasuke and Asura being Naruto. As such, Indra was revealed to be the ancestor of the Uchiha Clan and Asura the ancestor of the Senju/Uzumaki clan. At the end of Naruto we find that Sasuke had fully realized his Indra power and Naruto had fully realized his Asura power. The two had reached god-like power and together were even able to defeat Kaguya, their “grandmother”. But individually they were not unstoppable. For example, the Sage of Six Paths himself was likely stronger than Naruto or Sasuke if either were alone; that is why they needed to work together in order to defeat Madara and later Kaguya.
So, presumably speaking it is possible that if someone were to achieve Sage of Six Paths level power they would be able to defeat Naruto or Sasuke if they were unable to work together. Hashirama and Madara were the previous incarnations of Asura and Indra respectively. Hashirama’s cause of death was unmentioned in Naruto, however it is stated that Tsunade (Hashirama’s granddaughter) uses the same healing technique as Hashirama. It is also revealed that this cell regeneration technique has a downside – cells can only undergo mitosis a certain amount of time and as a result the technique shortens one’s life. This shortening of one’s life by overuse of the Jutsu may have been the cause of death for Hashirama, leaving behind Madara. I’m not saying that Naruto will die the same way but it is possible; he also may just get ninja AIDS. This could be a cause of death for Naruto, leaving behind Sasuke alone. Or the reverse could happen, Sasuke dying of ninja AIDS leaving Naruto alone. In any case, something will happen to separate Naruto and Sasuke allowing someone with SoSP level power to take them down individually. This is leading to the post-apocalyptic Konoha where we see Kawaki tell Boruto he will send him to meet the 7th (Naruto). Now who will have this Sage of Six Paths power level and how will they acquire it?