I have a feeling that both the House of the Crooked Coin and Heaven-on-High are tied to the Allagan Empire in some way. The architecture is very similar to what we've come to expect from it.

The former will potentially be a dungeon and the latter will almost certainly be 4.0's take on POTD.

I believe there's also a Xaela tribe that is said to have encountered an island full of steel monstrosities - that could be tied to the Allagan Empire in some way as well.