This was the same situation faced by the Islanders a few years ago.
-Traded for Vanek, sending their 1st (2014 OR 2015) to Buffalo.
-Had a terrible season, finished dead last in the division despite picking him up (and sent him to Montreal at the TDL, cutting their losses)
-Got the 5th overall pick, and kept it (drafting Dal Colle)
-Next season they made the playoffs and their first was 21 overall
So the Isles made the calculation "we can hardly be worse worse next season" and it paid off for them. I don't know if the Sens will definitely be a playoff team next year, but I think they will follow the same course of action, keep this years pick (assuming its top 5) and look to next year.
The critical difference, of course, is that the Islanders had a team full of up-and-coming young talent, but underperformed. Ottawa has definitely underperformed this year, and clearly had an anomalous run after they first traded for Duchene, but the EK situation is clearly a massive cloud hanging over them. If they are going to move him, and do it before the season they're essentially waving a white flag and signaling a major retool/rebuild. If they keep him for the year or until the TDL (assuming they won't extend him) they're killing his trade value.
That's a tough situation. With the same roster, I don't see them being this bad again.