Very brave move for Hunt and a smart one I think. He'll be an Aussie sporting legend if he becomes an AFL star.
I say smart move, because although the Melbourne media will paint this as AFL poaching one of the NRL's best, he hasn't really fulfilled his early promise. He's a solid player. Billy Slater and him vie for the QLD fullback slot and Hunt is more versatile and consistent but just doesn't have the brilliance. At QLD level you could say he is a picked as a utility player and for the Australian team he is nowhere near the player that Slater or Stewart are and picked in the past again for his versatility and the fact that Australia generally have enough flashy creative players and need solid defensive players to beat their opponents.
Think Daniel Wells in the sense that he came on the scene and built a big reputation but hasn't kicked on in the last 3 years.
As far as making it goes, I wouldn't be so quick to rule him out as some. He'll have the basic skills, is a good athlete and will probably have it all over AFL players in terms of body strength, tackling ability and possibly even some ground skills given that in rugby league you cannot fumble a ball on the ground. The things that will hold him back is endurance and things like being able to handball both sides, being able to raise his arms and handball out of trouble, overhead marking, spoiling and other footy smarts like not diving on the ball.