why does it matter? The focus is on this last upcoming book and I don't think a 10 year old boy will help rand defeat Shai'Tan [Although many japanese animes tend to think a "child's love" is more powerful than a nuke (Cough*gunparademarch*cough)]
You never read the hobbit have you? or the lord of the rings series? Oliver is already bigger then any hobbit and is being raised by matt and the band. I don't see any way Oliver could NOT play a huge role when so many of the main characters are tied to him in some way. And this "last" book is actually 3 books, Plenty of time for oliver to kill moridin. *gasp*