By my count, he has 3 RFA years left.
He is arbitration eligible. He will have a decent case because he's going to finish with 20+ goals and nearly 300 games.
Prompted by arbitration, Dzingel got a 2 year 1.8 million dollar settlement from the Senators with an inferior resume to Duclair. Dzingel while being the better overall player, is not anywhere near as skilled as Duclair. Although, Dzingel didn't have the mark on him of being as inconsistent as Duclair has been in his career.
I'd expect something in the 2.5M-3.5M range over 2-3 seasons. In Sens fashion, they'll backload the contract.
A two year deal might be a better approach if the Senators think they are just trying to pump Duclair up as an asset and dump him down the line. If the Senators want Duclair to be a long term piece, a 3 year deal is better because if Duclair comes in and plays hard for the next two seasons, then they probably feel pretty comfortable giving him a long term extension.
If they think he is going to be a star like he's looked like in this very small sample size, they could take a risk and sign him 5-6 years, which could put Duclair on a bargain contract if he pans out. I don't think they go that direction because as mentioned before, this is a player who has flamed out with multiple teams already. It'd be very risky.