Russell is a solid veteran. He's overpaid on the bottom pair, but he can play up the lineup so when there's injuries or another player is slumping he's a godsend.
I'm not sure why the Oilers would want to move him. He has a NMC contract, so maybe they just want to clear space for the sake of it? Maybe this summer is a good one for whale hunting.
Also maybe the plan next season is to find a more offensive minded D, and the team has no interest in moving Klef, Lars, Nurse, or Sekera. Plus perhaps Jones and/or Bouchard will be ready