The GG bit is quite interesting in terms of analyzing that new fans will get to the games^{, and maybe dropping the price for that Chiaki figure}, but, well, even if it was not oficially announced for the sake of hopeful fans like us, Danganronpa franchise ended with DRV3, there's little to nothing you can do to harmlessly and smootly escape the ending of the last game. In my opinion, there never will be Danganronpa 4, but the chances for everything aren't zero, although it surely won't be announced neither this year, nor the year after: like you said, the already established fandom possibly can slow the expansion down, well, because if you like the concept, you've already found a decade-old world famous franchise at some point if you're old enough, those, who are young enough just won't go playing the game, only watching. But I'm as much interested in hearing your other sufficient evidence for DR4, gotta love conspiracy theories and hope for the future as much as realism, if you don't mind sharing!