Who knows? Kishi's idol Toriyama claimed that he was only going to do one final volume, the Piccolo vs Goku fight, and he ended up going another 300 chapters.
But that only works for Naruto if we go the DBZ route, meaning some Kaguya Origins Storyline. Otherwise I doubt Kishi can pull out meaningful enemies from the current setting much longer. Currently we already get a recycled person meaning either Shisui Uchiha, Orochimaru or a really advanced White Zetsu whatever you like to believe.
A longer continuation would only work if he brought in some major league of baddies.
And the only ones I really can see that with the current setup fit that bill are Kaguya's relatives from whatever place(another dimension/outer space/hell/heaven.....) they may originate. Kishi although left that door wide open: Kaguya looks not really pure human, she had special powers before eating the fruit and why the hell would she need a slave army if she had the whole known world under control?
Compared to how Toriyama pulled off a whole spin-off just from a monkey tail and a green guy Kishimoto has laid quite some more groundwork.
