We've got four kids between the two of us. The two eldest who are Jason's stayed in UK. Sam who is now 20 lived with us for five years and gave him a choice of coming with us or staying and going back to live with his Mum. He was still at school at the time and said he wanted to stay on (wouldn't get a job). He is on our Visa but still in UK. Has been over for one visit but do not think it was for him. Talks about coming over when he falls out with his Mum but that is it. The way we looked at it was that he could come over in his own time. Would really like him to take advantage of his Visa and travel around OZ but do not think he is motivated that way and he appears to be enjoying everything at the moment, so fair play. We have ssid to him that if he comes over, to have an open ticket, in case he doesn't like it.
Jason's daughter who is 18 was a different kettle of fish. She gave Jason and I hell. She and I have never got on from the age of six unfortunately so things have always been slightly strained. Her Mum would not let both of them come. Tash would ring Jason up insulting him, leave nasty messages on our answer phone. Jason was going to see her the day before we left and she told him where to get off and said she never wanted to see him again and that he was a rubbish Dad etc. I got personal nasty emails from here saying that I had taken her Dad away from her and what she wanted to do to me. Two years on.... she sort of got over it - she contacts us when she wants money.
Charlie who is now 8, when we were coming over was excited one day and not the next ec. If he had had a bad day at school, he didn't want to come. Now he says he would only go back for a visit but he wants to stay here. He gets confused between events here and Australia.
To sum it up, I would say give him a bit of space and he may well come round. Try to get him his Visa and go from there. Like others have said on here, get him to try it and if it is not for him, just make sure he has somewhere to stay. Sometimes it is a bit of a knee jerk reaction like when you are a kid and you are told to do something and you think I'm going to do it regardless.
I hope for your sake he does come round, because he is missing one helluva opportunity.
Good luck with it