Could go both ways.
It was only mentioned that finding him/bringing him back will be a difficult task. Not exactly WHY it will be difficult. Knowing Oda, it could easily turn out that he simply is great at running away and hiding.
I think there's a decent chance Oda wants to throw in a twist with this son and actually make him a cool dude, who befriends Momo or something like that. That's the kind of stuff Oda loves to write.