According to Pro Football Weekly, David Hawthorne has signed a five year deal with the Saints. The Heater was a great find when he joined the Seahawks as an undrafted free agent, and for the last three year he's led the Seahawks in tackles and has just generally been a hard-hitting force in the middle of the field. However, injuries slowed him down significantly last season, and the coaching staff made no secret of its desire to add more speed to their starting linebacker trio this offseason. Seattle was interested in re-signing Hawthorne, but probably not for a contract as long term as the one New Orleans gave him.
2011 rookie KJ Wright was already the favorite to take over at middle linebacker headed in to next season, and Hawthorne's departure makes that move even more likely, but there's no clear backup for the position currently on the roster. Free agent Matt McCoy could be an option, assuming he's recovered from the knee injury inflicted by Aaron Curry that put him on IR last season, but the Seahawks may very well look to the draft for someone to back up Wright.