The next game is more than likely to occur a year or so after Ourai in Shaggai City.
Sakurai has been hinting on this for ages:
1. Sebastian ordered N'Ghakthun in Hypnos' bar, while M ordered Shaggai.
2. Crowley talking about Tesla can't enter Shaggai because of the rules that bind him.
3. The agent that recently sent the message to WIC HQ and warned them about Nephren-Ka is also located in Shaggai.
http://togetter.com/li/761444
So yeah, so something big is going to occur in Shaggai very soon.
BTW, Liarsoft mentioned that they have an upcoming game that'll be drawn by Ooishi (who did Inganock and Valusia).
https://twitter.com/liar_railsoft/st...777793/photo/1