Kishi won't let the goose go so easily.
Toriyama hasn't let go of DB an he's still going with folks still reading and watching.
Kishi will do the same, there's too much left out and too many who will want to do GT type Naruto along with the new gen.
Kishi can skrew this all up an people will still check it out and even pay to see it. As I said, just look at DB, a few character developements and the series is going on 20... 25 years.
Dragonball was able to come back because it was a very revolutionary and impactful anime/manga series said revolution and impact can still be seen and will likely never be forgotten. It hasn't been forgotten and never really was which is why it always sold video games and many other merchandise so well.
It can even come back from canonically ending after 30 years because of this.
Naruto on the other hand is not revolutionary nor did it make an impact the likes of dragonball's. So its safe to say it won't be remember as much.
Hell people are already dropping it in legions since the anime is what like 70% non canon filler most people dont give a shit about. Not a good reputation for an anime. And as for the manga well lets be real we all know the ending was not very satifactory or at least that's the general consensus.
The only merchandise it's really selling are those half assed storm games that get less inventive with each new installment. And that's just one game series dragon ball was selling games left and right.
In short, its very very unlikely Naruto will be able to pull a dragonball because its nothing like dragon ball. Dragon ball is on a completely different level than Naruto.