Of course some people are going to be disappointed. There can only be one! People attached to Harry Potter at first totally thought that Hermione would be paired with him. NOPE. That was totally crushed, and hundreds of people were sulking.
I don't know about clans being disappointed, but if Sasuke goes with Sakura, the Uzumaki clan won't be disappointed because Naruto brings too much honor to it.
Speaking of which, I predict an overload of traffic will come to NarutoBase if Sasuke does get paired with Sakura. There's going to be so much fan action, literal **** will hit it.