In addition to Austria, Italy and Switzerland I have now confirmations for Nikon press events on September 21st in China, France (see above screenshot) and Romania where the event will take place at the National Modern Art Museum in Bucharest. Nikon is really putting a lot of effort into the next announcement. I will repeat again: I do not expect any DSLR announcements on September 21, just the new mirrorless system.
Update #1: there will also be an event on September 21st in Nikon's head office in Pretoria, South Africa.
Update #2: and another invitation from Germany: "We invite you to learn about the Nikon Professional Products and perhaps to also find out what you can look forward to":