The Danganronpa series has become sort of a cult classic this generation and fans can’t seem to get enough. Series writer Kodaka Kazutaka in a recent talk with Polygon confirmed that Danganronpa 3 is indeed being worked upon.
Kazutaka mentions that the game is in “very early development” and in this state it is common for game’s story and characters to change several times.
Until everything’s been written, there’s nothing that’s set,
So to answer your question, it’s still very early because the scenario isn’t written yet.
The Danganronpa series started on the PSP in Japan where the first two games were released. Last year both games were ported and localised for North America and Europe. This means Danganronpa 3 will be build for a newer device in mind and will not be a port.
The original Trigger Happy Havoc and its sequel Goodbye Despair received both critical acclaim and excellent sales. Developers Spike Chunsoft are currently working on a spin off titled Danganronpa: Ultra Despair Girls which is set to arrive on the PS Vita this Fall.