I think there was too much effort put into Gaara for him to be a one-time character.
One thing Kishimoto-sama does very well is to create not just a few characters, but an entire world filled with characters that feel real. You feel like every character has a full backstory to them, not just the main characters. I doubt, that with as much of Gaara's story as was revealed, that he won't make a return appearance.
It seems to me that the first appearance of Naruto was to teach Naruto some lessons about fear, love and protecting others. (One of the reasons I LURV Naruto vs. Gaara so much.) Gaara also got some lessons taught to him by Naruto as well. I think he'll come back when there is something else Naruto needs to learn from him, and/or vice-versa.