Okay, this is speculation but, June 8, 1984, Ghostbusters was released, June 8, 2019 is a Saturday, and Planet Coaster updates have had the propensity of being released on Tuesdays, so it could be June 11, 2019 still in time for a 35 year celebration of Ghostbusters. Or it may be the 30 year anniversary, when Ghostbusters 2 was released on July 15th,1989; however July 15th 2019 is a Monday, but still close enough for a Tuesday release. OR it could be like when Frontier released their Jurassic World Evolution game at the time the sixth Jurassic movie was released, then that would mean Next Year when Ghostbusters 3 is released, because somehow the Ghostbusters movie with the woman does not correlate as part of the "sequels". Ironically is the fact that this "Ghostbusters" promotion is just an UPDATE to a fixed game, not an entirely new game, so it still anybody's guess.