@Azure: I know you've gotten plenty of other replies, I just wanted to add my own two cents in

Yes, Kishimoto could just make SasuSaku and NaruHina canon easily if he wanted to; as you said, it wouldn't be quality writing, but he could do it.
But is it likely, compared to the likelihood of him making NaruSaku canon? No.
NaruSaku has more manga evidence supporting their relationship eventually becoming canon than SasuSaku and NaruHina do. NaruSaku is the only relationship of those three in which the object of unrequited love has shown on multiple occasions feelings that go beyond friendship. Has Naruto ever blushed over Hinata (not in response to a compliment like in her proud failure speech - which is not romantic given he had the exact same blushing response when Jiraiya compared him to Minato)? No. Has the strength of Sasuke's feelings for Sakura (or Naruto's feelings for Hinata) been commented on by a third party? No. There simply isn't anything to indicate that Sasuke or Naruto feel anything beyond friendship for the girls respectively, while he has gone out of his way to depict Sakura's non-platonic feelings for Naruto on multiple occasions.
And then when he gets to make a movie, he trolls NH (using Hinata's feelings for Naruto to emphasize NaruSaku - her being jealous of Sakura's close relationship with Naruto) and SS (depicting Sakura's feelings for Sasuke as pretty shallow - or perhaps naive as Ciarhda said before and having Sasuke treat her just like any of his other fangirls) while developing Naruto and Sakura's relationship, having multiple people (including Menma's parents) think Naruto and Sakura are going out, has Naruto asking for dates from Sakura, having Sakura blush over Naruto when he saves her bridal style, and then saying the whole thing was the longest date ever at the end.
That's not even taking into account the parallels coupled with the new generation surpassing the old theme.
So again, Kishi could make NH and SS canon based on what he's given in the manga thus far -- in fact, I'd even expect it if he didn't develop and focus on the NaruSaku bond as he has. But since literally all of the evidence seems to point towards NaruSaku in terms of focus, mutuality, and development I think its only logical to think that NaruSaku is the most likely to become canon at this point over the other two.
Edited by Paptala, 21 October 2012 - 08:24 AM.