Its possible. But if they can move Spezza they can keep Seguin. That'd be a hell of a trade
Would be tough to make it all work for next year though with Seguin's raise, Karlsson's, signing whichever of their RFA (Ritchie, Shore, Janmark, Lindell, Honka) that are not traded.
I ran a quick number crunch and they would be at $80 million if they signed Ritchie, Shore, Janmark, and Heatherington to deals totaling $14 million between the 4 (suspect Honka going back to Ottawa as part of the package). Add in Lindell getting a bump to ~$5 million (double what he makes now) and Karlsson at $11 mil and Seguin at $12 mil and they are already at $80 million on the cap next year and would still need 2 more D and a forward or two to fill out the roster. I expect the cap somewhere around $82-$84 million next year so finances would be quite tight.