Sorry for the long post - but all these comments are spot on.
WE DIDN'T READ IT WRONG. Please don't buy into that. This is exactly why this movie has been made.
Every creator makes choices about how h/she wants their work to be interpreted. NaruSaku is handsdown the most supported, foreshadowed and developed pairing in the whole 15-year creation. If you doubt this any of that development, then look at the fact that Naruto never stopped loving Sakura. Ever. Not once. Even his last words in 698, as the Naruto we knew and recognized, were "Thank you, Sakura-chan," words which are only ever used in a statement of love in this manga.
As part of a huge international brand, Kishimoto the author is a very small part of the larger picture. He is a cog in a very big machine. He's an important cog, to be sure, but he's really, really small in comparison to the whole thing. The only part he has any control over is the manga. That's it.
These are all handled by other staff and outside sources:
Manga - publishing, distribution, marketing, and the merchandise plus its advertising and marketing
Movie - written plot, casting, animation, marketing, scheduling of interviews and advertisements, ticket sale and promotions, and sales of merchandise, plus its advertising and marketing
- and this excludes all other ancillary staff necessary for getting that manga out the door.
Even though Kishimoto is sitting atop the one of the world's most popular manga, he has very little control of what's underneath him. And if its determined that the brand will make more money going one direction instead of another, then that's the direction they're going to go, whether Kishimoto wants to or not.
And there is no way Kishimoto would ever be allowed to go out into the world and speak against the direction. Not if he wants to keep being on the payroll. And he knows understands that completely. Naruto is a BIG BUSINESS.
My point to this is that the manga, the one thing that Kishimoto has the most control over, was written for NS. Over and over and over again. Even up to its ambiguous end. I think at some point he knew that the ending was going to have to go toward NH. Whether that was 8 years ago or 2 we may never know. But he celarly had opportunities to build in NH and SS in a way that it didn't feel like a betrayal. Yet he still didn't. He continued to reinforce Naruto's connection to Sakura.
I think he wrote what he wanted, sprinkled in enough Hinata interaction to string that story along (knowing there would be a movie in the future about it), and when it was time to end the manga, he tacked on the last two chapters. There is ZERO SasukeSakura development. There is ZERO mutual NarutoHinata development. There is consistent Naruto Sakura development.
Honestly, I think Kishimoto just gave up on his story. It's clear to everyone that any semblance of a plot stopped after the Pain arc. The war arc was nothing but filler character after filler character, with the sick train wreck of Obito's story in the middle.
But Kishimoto could have developed any ship he wanted, yet he didn't. He chose to steadily build on NS. That lie of omission — not developing SS or NH when he had years to do it — tells us something: That NS was not as far behind as he claims it was. And interviews that sound conspicuously like damage control are not going to change that. His actions here speak a lot louder than his words.
He may be a sexist human being, and he be an author who royally f*d up his story in the end. But the NS development was there, consistently, steadily. From beginning to end. And that was Kishimoto's choice to include it, reinforce it, parallel it and foreshadow it.
And if this was a truly happy ending, then Kishimoto would have drawn a happy Naruto finally achieving his goal. Hokage with Sakura on his arm. But he didn't get it. And so Kishimoto didn't have the stones to illustrate anyone getting a romantically happy ending together. Not NH, nor SS. He just let it all fall apart, and the movie people will put together a new storyline out of the pieces that are left over.
I feel a lot of things about this ending: heartbroken, angry, disgusted, etc. But one thing I absolutely don't feel is wrong. NS is there, all the way through the manga. And the statement that fans were reading it wrong is just a lie to sell people on the movie and the new series that will spring from it.