I don't think they would spend so much time/money/energy introducing new characters, creating manga chapters/oneshots and a movie if the DIDN'T plan to continue.
They aren't extending the series past the end of Naruto to satisfy the fans. They are doing it to make more money. And as long as that carrot is still out there (which it obviously is) they'll continue. Otherwise why go to this effort?
The original characters have been redesigned from Kishimoto's manga style. They have a new look, new hair, new lines on their faces. They don't look like the Naruto characters we've known.
And the next gen already look different. (And I think there's been another illustration team working on the series for a while.) So everything is in place to continue on with the series just under a different hand.
I'm curious to see what the official word is, but they made it clear a while back that Naruto would continue in another 'phase' (can't remember what the term they used was).
I can't imagine they'd put all this effort into a next gen movie, then end the series just when the momentum gets going. After all, it's infinitely cheaper to produce black and white manga chapters than it is to make a movie.
So I wouldn't be surprised to see an announcement come out just after the end of the movie run that the next-gen series will continue in some form. It's exactly what they did with "The Last."