I think it's pretty unlikely that you won't be getting massive offers for Rakell or Rust this off-season. Sure, if the offers are shit don't trade them just to trade them, but I think it's by far most likely that the offers for them will be good.
It's not just about acquiring futures for them, it's also about turning those futures into other young pieces to help the team in the long-run. In a perfect world, you send out all 3 of Rust, Rakell and Karlsson while adding at least 2 quality young NHLers (ideally Byram and a replacement top-9 winger) and additional futures. The goal should be to do something really aggressive like:
-Rakell to LA for Spence and pick #24
-Spence, Rust and pick #24 to Buffalo for Byram, Quinn and pick #39
-Karlsson to Carolina for Walker and a 2026 1st
You're basically turning Rakell, Rust and Karlsson for Walker, Byram, Quinn, pick #39 and a 2026 1st.