The idea of connecting the two "Fantasyland" via the Frozen mountain would be amazing.
However, I'm a little doubtful, as Tokyo has a very large crowds, and I think that's why they generally don't allow park hopping (or as of day 3 in your stay). For a very large premium though, maybe they would be tempted to offer that.
The footprint of the expansion is massive. I reckon the next move is around Rivers of America, once all parkings will be built on...