What you say is true, and, perhaps in due time he'll change his mind. In the meantime, he's excited, he's reborn and found vigor. What more can you ask for?

Sure, at some point reality will dawn but I'm sure he'll have learned a lot and will have a lot to add if he ever moves back. Or he may stay, a perennial outsider he may remain, but finding purpose in a place he might find impact. My main wish is that he forget the expat community, leave it behind and get mixed in with the locals. Too many expats (immigrants) hold on to their communities too long and fail to discover the true host country.