Apparently, Warner Bros Movie Land in Australia is getting an Oz themed section with two rollercoasters - which i hadn't known before researching the topic - and i'm not sure if that complicates things further, being outside the U.S., but i can only assume it does.
That all being said, i do want to say that IF IT WERE TO HAPPEN, it *should* be an addition to Islands of Adventure out of the three parks:
ONE because it doesn't fit the studio/backlot nature of USF as well as it does the other two,
TWO because EU certainly won't need it or the attention of it anytime soon,
and THREE because Islands of Adventure is still a park where everything there is based off of stories; whether literary or mythological.
Until solid ground is broken on anything replacing anything in IoA, i'd like to see them continue with that theme and OZ would be perfect for that.