The 23-year old has emerged as a target for the likes of Derby County, Italian club Catania and Scottish champions Celtic with Arabs chairman Stephen Thompson confirming he will be departing Tannadice in the next transfer window.
"Johnny won't renew or extend his contract. We've been told that by his agent," Thompson told the Daily Record.
"So it's a situation where we've got to look after and protect the club which means we should be selling him in the summer.
"An English club has made a bid. It's not quite what we'd like and others have spoken to us. We've decided to keep things private and not name clubs.
"One did come out a number of weeks ago, which was from Italy, and we turned it down."