I thought maybe Tokyo because at Comic-con Martin Wood suggested that it gets partially destroyed, so I think the major showdown between the Cabal (with Ashley) and the Sanctuary team probably happens there. I think that's where Helen and Druitt are going to 'storm the castle'.
The very last clip looked like Druitt running into Helen while jumping away in the central room of the Sanctuary. Maybe Helen built all of the Sanctuarys with a common central room, but different exteriors.
This is pure speculation of course, but maybe Helen and Druitt go to Tokyo to stop the Cabal and save Ashley, and in the process there's an explosion or something that destroys that Sanctuary. Druitt is able to save Helen, and maybe Ashley's fate is left unknown as to whether she was able to jump away in time. In the comic-con trailer there's a shot of Helen and Druitt sitting in ruins with him says 'what now,' so maybe they're at the ruins of the Tokyo Sanctuary wondering how they're going to find Ashley now. I believe they return to Tokyo in the S2 finale, so maybe that's when we'll see the return of Ashley.
Argh, it's going to be a frustrating month.