Gaara can't become Naruto's rival...
Naruto is merely starting to gain strentgh and power, Gaara is already at the end of his line (he didn't develop much since age six), While Naruto would have more and more raw strentgh and chackra, all gaara can improve is his self control and taijutsu skills.

it's like how Tien couldn't touch Goku after the second tournament...


anyway, Sasuke will stay the eternal rival in this story, Maybe he'll go X and kill Sakura... that seems like a good ending for her!