Well, here are some of the things Rama will be involved in from now on:
1. War against Lavanasura
2. Coronation of Shatrughan
3. Stories of Budh, Hila, the dog, etc (they may or may not show it)
4. The Ashwamedha yagna
Aside from this, they could, if they wanted to, show Rama when his nephews are born (I don't exactly like Uttarkand renditions where only Kush & Lav are born, but their cousins are totally ignored). They could show those kids growing up as well at the same time that Kush & Luv are, and after Sita's passing, they could show the balance of Rama's reign, including his procurement of kingdoms for his nephews and sons.
Plenty of Rama left, depending on what the Sagars want to cover.