Pittsburgh is really the place that makes the most sense for Karlsson. Ownership isn't going to allow Malkin, Crosby, or Letang to go anywhere else. They want to try to contend with that group (which I think everyone believes is logically over, but a last hurrah sort of thing). They need a guy who can take some of the load off Letang. They have some bad contracts they could toss San Jose's way to eliminate or at least lower the need to retain.
Granlund + Petry for Karlsson (0-1.5m retained) could be the basis of the salary side, then have to figure out the value from there.