Here's what this trade looks like:
To Oilers:
2020 second round LW Roby Jarventie, 2025 fourth round draft pick
To Senators:
2021 first round draft pick C/RW Xavier Bourgault, 2021 fourth round draft pick RW Jake Chiasson
Bottom line - For the Sens, a team not currently in win-now mode, they can afford to take more time with Bourgault, who suffered a shoulder injury last season which explains a dropoff in his numbers. Although the Oilers were wanting better from this player by now, they are in win-now mode and can't wait to see if Bourgault regains his form, especially since they've already had a couple of cap dumps in Foegele and Vinnie Deshairnais and ideally it would be better to have cheaper prospects in place to take the place of the more expensive veterans they let walk, and the Oilers are hoping Jarventie, the most NHL ready player out of all of them, can make that leap in the next couple of seasons.
He only played 22 games last year for the Belleville Senators but made them count by putting up 20 points in those 22 games, so there are injury risks with this player as well. Jarventie also had a short seven game stint with the Senators earlier this season so has already had some (although not much) NHL time. Chiasson is a mid-round pick who is essentially a throw-in because, in his first pro season, he's put up rather pedestrian numbers. This is an even bigger project that have even more time to grow in Belleville with less pressure, or even for their ECHL team the Allen Americans.
The fourth rounder coming from the Senators will be a welcome additional pick as the Oilers are short on picks for 2025, pending of course any other transactions that come their way. Currently, for next year the Oilers have no first round pick (traded to Philly for this year's Florida Panthers first round pick so they could draft Sam O'Reilly), no second round pick (the last draft pick going to the Utah hockey club in the Zack Kassian trade), and no fifth round pick (gone to Anaheim in the Henrique/Carrick trade last deadline). This trade now leaves them with their third round pick, two fourth picks including their own, and their own sixth and seventh round picks. Those of course will likely change as time goes on.