Okay so it's become a bit of a theme that Naruto surpasses all of his peers and teachers through hard work and dedication. That's the gist of it, he surpassed Kakashi, Jiraiya, Minato and probably Killer bee too. The theme kishi is portraying is that the next generation always surpasses the old one but then we have Madara & Hashirama recently. They're literally the stuff of legend and their power levels are ridiculously out of scale with everyone Naruto has learnt from so far.
So it's very possible/likely that Naruto will gain a new power up or ability to overcome Hashirama. That's the pattern but it looks unlikely anytime soon considering how much Kishi is pushing in our faces how strong and compassionate this man was. So...little theory- what if Naruto DOESNT surpass Hashirama in terms of pure strength alone like he has with his other sensei. What if Naruto is just the one to bring about peace and that's how he surpasses him. Doing what he ultimately never could? Just a little thought.