According to Barry Toohey he is set to Re-Sign for 2 more years! http://www.theherald.com.au/story/5315255/knights-on-the-verge-of-re-signing-king/?cs=2503
Brown is picking his most experienced players for very good reasons early in the season (because experienced players will blend into a new team much easier), but I think King would be picked ahead of Heighington at least if he were picking on form, and I think guys like King, Yates, Stone and maybe Brodie Jones will get a chance once the team is a bit more settled.
Imo Heighington has been playing some good footy for us his experience has been very telling in a lot of situations but I'm glad we resigned King I'm a bit of a fan off his as i like his aggression , when he tackles he likes to try to hurt the opposition . His running game still needs a bit of work but he is young and that will improve over time .