We had seen the 7" scale Real Ghostbuster figures from Diamond at Toy Fair 2018 and also knew that these 6 figures would make up wave 9 and 10 of the Ghostbusters series.
We were not sure of the wave breakdown, but that has now been confirmed with this promotional image of Series 9 which is made up of Egon, Winston and a Real Ghostbusters Cartoon Slimer. That puts Series 10 being made up of Peter, Ray and the Stay Puft Marshmallow Man. Collectors will need to get the Build-a-Diorama parts from both Series 9 and 10 to combine with the ones from Series 6 to 8 and build the Ghostbusters Firehouse diorama.
Series 9 is scheduled for a late 2018 release with pre-orders due to go up soon.