This is the only thing that makes any sense about the reasoning for this ending, period.
To sit there and say "I decided it a long time ago." yet 50 some chapters ago we were still getting NS and anti SS is complete and utter BS.
Damn straight. Those of us who have REALLY questioned his actions of late, we can tell it's likely he caved into popular demand rather than to just do what he was showing.
There's a fitting trope for this BS that a friend of mine named Erin did when she ranted on why Sorato in Digimon Adventure 02 doesn't work, shouldn't have happened, and was bad, clumsy writing, which fits so well into this scenario with NaruHina right now; http://tvtropes.org/...dByTheRedString
She also had it best for that same topic which can apply to the ending of Naruto with sudden NaruHina and SasuSaku. Hang on, lemme post what she said on that kind of thing.
There is a saying that goes, "Show, Don't Tell" and "Actions Speak Louder Than Words"...Sorato did neither of these things. Just a couple they threw in our faces and expected us to take it at face value, when they had nothing to show for it to the audience that we should take this couple seriously. You can't just throw people together and ASSUME everyone will agree with it. For ANY relationship to be believed by an audience of your story (and I mean any relationship-not just the romantic ones), you have to show the characters interacting together-showing them grow together, showing them be influenced by each other, positive or negative. With Sorato...we pretty much got neither...just two random names they pulled out of a hat and decided to make them an endgame despite the fact they barely interacted, grown together or influenced each other.
Just replace Sorato with NaruHina, and there ya go! In all honesty, that's what it feels like Kishimoto-sensei did with so many of the couples in the end of the manga, which is why several of us are mad besides how it feels like he just took a dump on all the development he spent 15 years working on for everyone just to say "kitten it, I'm done!" or something like that.