I examined PART of the map (there are four parts to the overall Spirit Tracks map, just as The Advetnure of Link's map could be split into four parts), and it nicely matches up with the, say, upper left part of The Advetnure of Link map.
Another non-Hyrule reason- the trailer shows mountains and forests everywhere, so big it needs train tavel, and there isn't a coast, but a river and more land.
Again, don't assume anything. To assume it's the same land as AoL is definitely too much assumption. However I see your point about the island. I'll admit it a possibility.
It is fact. You see a very big ass Hyrule in Spirit Tracks, one that need strains to get around, it also appears to be set in part of The Advetnure of Link's overworld, which was very big and watery.
And don't go 2d vs. 3d. Hyrule always looks smaller in the 2d games. And there is nothing to say that old Hyrule wasn't a large island, too.
The Minish Cap's Hyrule is surrounded by forests and mountains and is set on a BIG ISLAND. Old Hyrule is surrounded by the same thing, and because it is 35, you can't see beyond the mountains: the water.
It wasn't the coast. It was the view of it as an island. And we don't know enough about Spirit Tracks yet to be making claims like that. Although it can be assumed, don't claim it fact.
Spirit Tracks shows that the New Hyrule is a huge landmass, not an island. There is also no coast in The Minish Cap's Hyrule, and it is seen as being surrounded by mountains, forests, and rivers. In fact, the New Hyrule is so big that is requires trains to get around.
In original intent, The Legend of Zelda's Hyrule and Ocarina of Time's Hyrule were supposed to be the same- one had a coast and the other didn't. It shows that the coast means nothing to the developers. Either you see the coast, or you don't. But it's there eventually somewhere in the south east.
