Destiny 2 has been released almost two years ago and it's still being supported with no content. At the same, it seems like Destiny 3 is already in development, and it will be released somewhat soon.
AnonTheNine, a well know Destiny 2 leaker, has recently revealed some information regarding Destiny 3. According to the leaker, the game will be much harder than its predecessors, and it will cater to the hardcore audience, expanding the role-playing game elements of the series. The game is apparently releasing next year on PlayStation 5 and Xbox Scarlett, but it's not yet clear if it will be cross-gen release.
The goal of D3 is to cater to the hardcore audience more than anything. This game will be supposedly much more difficult than previous entries, and will very much focus on how the hardcore community of the franchise will play. D3 will also provide more RPG elements in it's approach design compared to previous entries in the franchise.
These decisions, apparently, are all some early development ones, so they may change in the final release, according to the leaker. As it always is with rumors, we must take everything with a grain of salt until an official announcement comes in.
Destiny 2 is now available on PC, PlayStation 4 and Xbox One.