I'm personally hoping to see Petaia develop into the form Australia 13.
I know I have argued against wingers/fullbacks/etc. being played at 13 in other threads, but the thing that really gets me about Petaia is his defensive positioning and ability in the tackle. Those are the trademarks of a great outside centre.
On top of this, he's clearly a massive talent in other areas, such as his powerful running, tactical kicking, and his catch-and-pass skills. These things combined could make him a truly world-class 13.
However, worst case, he won't be given a continued shot there and will just be a great winger/fullback. Also clever work by his agent to have the contract expire the year before a world cup; watch as Rugby Australia throw the kitchen sink to keep him come 2023.