Since the anime is catching up to the manga, if there were to be fillers, I'd like them to at least be useful fillers. For example:
1. Show history of the fourth.
2. Show history of the sannins.
3. Show history of Naruto's birth.
4. Show white fang (kakashi's father) in action. Why? It gives us a reason as to why Kakashi must be a genius.
5. others listed in previous topics and discussions.

Something to this degree would be nice. Fillers would be the best and most opportune time to get history out of the way. I hate fillers where they go off on some distant tangent that totally destroy's the story line e.g. Kenshin.