Along with Alan Rogers, David Johnson and Kevin James, King and Nowland were told not to join the club's pre-season tour of Denmark.
Johnson held talks with League Two side Lincoln City over a move, but the Imps pulled out after his £10,000-a-week wage demands.
But King and Nowland could be set for new clubs sooner rather than later.
Megson said: "It's starting to pick up a little bit. There have been one or two enquiries for Marlon, and one or two clubs have enquired about Adam as well.
"I'm sure over the next couple of weeks there'll be even more interest shown in the players."