I think Sakic is best served by waiting, even if it means eventually losing out on a big return or eventually losing Duchene for nothing altogether.
He's not producing like they want, but they aren't going to get an equivalent piece for him while he's slumped. Duchene is far from being a cancer, there's no rush to move him if they are best served by waiting.
I totally empathize with other GMs as well. Why give up a big piece for Duchene and open a hole in your roster if he isn't a big upgrade elsewhere.
At this point, I think the Avs might be best served by targeting another player in a slump for value rather than going after a prospect/young player that might be at the "peak" of their value.