I'm pretty sure they weren't talking about Rookburgh itself featuring a hotel, but Rookburgh being the first step towards a 3rd hotel. Remember, they still have that unused plot of land behind the Kaiserplatz (called "Obstwiesen") which has almost exactly the acreage of Hotel Matamba, and think about it:
Yeah they were. There has been a lot of speculation about a hotel in Rookburgh primarily based on the teaser from the Rookburgh sign - "Discover a new dimension of the interplay between themed world, attraction and experience by day & night".
I do think a hotel is the most logical explanation for the teaser staying overnight in Rookburgh is the only way
one could truly experience the area by day and night.
Of course a Rookburgh hotel could not take up as much space as Ling Bao or Matamba with their gardens etc. But it would be far more suitably located than the obstwiese site as it would have direct access to the main road and guests could park in Berlin car park opposite.
However I'm not completely convinced by the idea of a Rookburgh hotel I can't see it fitting, unless they demolish the admin/office block next to the Berlin entrance. After having seen the new hotel under construction at Blackpool Pleasure Beach last month I'm confident a similar hotel could fit in PHL. Its site (excluding the Restaurant & Bar in the former Coasters Diner building beside it) is only slightly larger than the site of the Admin Block in Phantasialand. Despite its relatively small footprint the BPB hotel will have 120 rooms, including 10 suites, and a conference centre.
However Phantasialand have extra space with the back end of the Rookburgh site as well the admin block site to make a hotel larger than BPB's. (There was also a suggestion on PhantaFriends.de recently that they could make a Rookburgh/Berlin hotel there even bigger by replacing the Berlin entrance with part of the hotel above it. Not sure how feasible that is though.)
The hotel would also then serve as a thematic backdrop to the Rookburgh area, just as Matamba and Ling Bao do for their respective areas, instead of having a one-sided themed facade wall as Klugheim has.
I 100% agree with your ideas for opening up Berlin for resort guests and a hotel on this site would then also have direct access to Berlin.
Only issue with that theory is they would need to demolish it soon to start construction for a 2019 opening. Perhaps in November when the park is closed before the Wintertraum - a lot of offices are already in Hotel Matamba, the remaining ones could be temporarily relocated and then moved into the new hotel when done.
However if this building doesn't get removed in November then I struggle to see how a hotel could come to Rookburgh even though I think it is the most logical explanation for "by day & night". Maybe some other form of after park hours resort offering will be Rookburgh explaining it.
This connected to what Fluorineer said, I expect
a new main entrance behind the Kaizerplatz
with a hotel on top of it, just like Disneyland Paris because all the parking lots are now on this side of the park.
An entrance behind Kaiserplatz is just not feasible. The small gate in the middle is for fire engines and vehicle access but is far to narrow for mass crowds of people. Also guests from there would be unable to get in during Wintertraum because of the ice rink.
Guests could come in above into the arcade passage at the very back but from the outside this quite a height and sending people up two storeys via steps isn't a very attractive main entrance.
The main car parks are not on that side of the park by choice. PHL simply have no other option as they don't own the land around them.
PHL's most recent expansion plans featured a massive multi storey car park opposite Berlin/Fantasy. This would suggest they hope to force the owners of the Mystery and China car parks to sell the land (as they would no longer be making money from parking) and then they could expand the park there.
The Obstwiese behind Kaiserplatz will certainly be for future expansion but I'd imagine an enclosed attraction of some sort one day there. It would also make the least noise given the neighbours right behind it. Once the Taron overflow queue is removed they could open up a small plaza there between Klugheim and Mexico and the entrance to the new Obstwiese attraction.