I honestly think a lot just because Ottawa is virtually in control of the market. If I'm Dorion, I deal Stone to Winnipeg and that would force Nashville to make a run for Duchene/Panarin, and we already know there's a zero percent chance of Panarin staying in Nashville so I think they try to go for Duchene first.
In terms of the isles, I don't really see it happening without Dobson/Wahlstrom/Wilde, which you should only deal 1 in Stone/Dutchy are extending in Long Island.
No idea what a rental package would look like, but if there's an extension, I'd settle for nothing less than Noah Dobson as the main piece. No matter what. And I know Isles fans are super hesitant to give him up (I would be too, he was my favourite prospect from that 2018 draft). But I think Duchene would be a huge add if you could lock him up. Barzal-Duchene can run against the best of centre duos in the NHL.
But back to the original question, I'll guess they each go for an A- prospect and a 1st, with a few conditional picks if they extend there.