There's significant internal growth that can still happen. Brown, Tatum, both Williams, Nesmith, and Pritchard are are not done becoming the players they will be. Fringe NBA players like Fitts, Hauser, Thomas, and Ryan may all develop into role players as well (good organizations should expect 1-2 of these every few years). I'd even argue that White might continue to develop as a player as well. I think Smart is mostly who he is (obviously Horford too).
I'm not sure the mindset should be to shake things up. If there is a high-level playoff rotation player that can make the team better, the Cs will consider it just like any team.
The other thought is whether or not the Cs believe Horford can play at the same level for another year. If not, then the time to sell him high to a team that has playoff aspirations is now.