Matt Duchene loves the Habs (he grew up a fan and still says he loves playing there according to recent videos). Why would Bergevin trade the world to get him 4 months earlier when he can get him for free? Marc Bergevin won't be stupid, he'll trade for a "rental" Duchene because he knows Duchene will extend here. No way Ottawa gets Suzuki nor Poehling for Duchene. Maybe you'll get Juulsen, if you're lucky, and a pick.
Besides, it was known that Bergevin turned down Poehling+ for ROR, why the **** would we trade Poehling+ (who's way better than he was last year) for a rental who would easily sign with the Habs come July 1st?
Juulsen isn't a good base; he is injured and while people are confident he will return, until he actually does and shows he is fine, his value is tanked.
You trade for a player like Duchene now because we are very likely a playoff team. Sure, we could get him in Free Agency, but the price of free agency is generally 20% more because you have other teams bidding and you get one less year.
Duchene will get 8.5-9 x 8 or 10+ x 7 --- I would happily trade one of our prospects for him if we get the cost certainty, especially with the value of cap space in today's NHL.
I would trade Poehling due to the NCAA loophole far faster than I would trade Suzuki, who likely joins the big club next year.
Poehling + Alzner + 2019 1st + Hudon for Duchene (sign and trade) and Dzingel (rental). We clear some cap space, we get a top 6C and a rental winger to bolster our offensive corps for a run this season, and the Sens get a top fledged prospect.