New voice actors?

[Kraco]

But with the exception of Naruto, perhaps, the characters already have voices better suited for older characters. So, actually the situation is reverse: for the most part the voices become more fitting.

It remains to be seen how well the older Naruto / his voice match. Perhaps the actress can adjust her voice accordingly and perhaps Naruto won't behave so much more maturely that there would be a clash.

I think it might not be easy to find an actor who could convincely took over the part, and everybody would think it's a natural change.

[XanBcoo]

I'd be satisfied if Juunko Takeuchi played Naruto after the time jump, just with a gruffer or deeper sounding voice. 15 isn't that much older, but like others have said, it's after the time a young boy's voice breaks.

[Kraco]

I'd be satisfied if Juunko Takeuchi played Naruto after the time jump, just with a gruffer or deeper sounding voice.

Maybe the real reason for these long filler seasons has been to give Juunko Takeuchi time to undergo a diet of raw whiskey to get her a good rasp...

[XanBcoo]

Perhaps she's also started smoking in order to create that 90-a-day sound that Maille Flannigan brings to the role...