I know Wigan have first option on Sam, but it will really depend how Sam felt if another club offered him more money, and as he was on a 3 year contract with the N,Z, Warriors a fee would probably have to be paid to them as well.
This evenings M,E,N carries an article with the Sam wants to come home story and it says that the good Dr of Salford would be very interested, especially if the Marquee player exemption was implemented in July. I seem to remember it being reported that the good Dr approached Wigan with a million pound bid for Sam prior to Sam going to N,Z, which means it could prove to be a bit expensive for all concerned if Salford enter the race for Sam.