Okay, I did a little time travel back to Lorelei in DoA3. Yes, it is definitely that stage, just a little spooky-fied with dead trees, that giant red moon, ravens and gargoyles and instead of the vases on the highest floor, we have those orange lamps. There will be different floors (for everyone, who was afraid, there wouldn't)!
Comparing the old well of the original with the one behind Kokoro, one can confirm, that Team Ninja wasn't as lazy as I thought. They used more detailed polygon structures and the texturing is completely new. (I really thought, they were going to give us the exact old stuff...XD)
The moon completely switched places in the Halloween-Lorelei version, which I find interesting, because, from an artist's point of view, the moon had the perfect location in the original version. The preview tracking shots, as we so far knew them, won't work like that anymore...
Another thing I noticed: They might have completely changed the scenery around the castle. In the Twitter pics, we got so far, I can't make out the river or the other castles and houses, like in the original version. So, this stage might be closely modelled after Lorelei, yet still be a completely new location.