The 24-year-old joined the Wildcats on a three-year deal from the Warriors for the start of the 2012 season but failed to cement a spot in the team.
Wakefield coach Richard Agar said: "He has got a club in the NRL that he's going to go and join one of their full-time squads so we've agreed to release him with immediate effect."
Reports suggest John will link with former coach Ivan Cleary at the Penrith Panthers.
John said: "I am very grateful for the club to allow me to leave. The move didn't work out as well as I hoped and I'm really looking forward to my new challenge.
"It was a mutual agreement between both parties that we would part and I've left on good terms. The Wildcats have acted really professional."