Here's a translation from Kishimoto himself!
"Studio peridot is working on a new anime segment detailing Hirizens best years as a shinobi, this ark is basically to show just what he meant to the leaf village and the shinobi world and his level of unpresidented power. Some people really didn't believe me or want to accept what I said when I said he was the strongest hokage, well this series is apart of our main continuity so it is what many americanfans refer to as "cannon" and any abilities displayed will be relevant to the main story."
I'm so excited for this as a Hiruzen believer.
"Studio peridot is working on a new anime segment detailing Hirizens best years as a shinobi, this ark is basically to show just what he meant to the leaf village and the shinobi world and his level of unpresidented power. Some people really didn't believe me or want to accept what I said when I said he was the strongest hokage, well this series is apart of our main continuity so it is what many americanfans refer to as "cannon" and any abilities displayed will be relevant to the main story."
I'm so excited for this as a Hiruzen believer.