Risk of Rain 2 has been announced in a developer update released on the 8th of May. Risk of Rain and DEADBOLT developers Hopoo have announced in addition to the sequel being developed, Risk of Rain 2 will move from 2D to a 3D engine.
Developers Hopoo state that the game has been under development for six months, but is still very early in development.
Some gifs showing the game in this early stage also accompanied the announcement:
No release date has been set for Risk of Rain 2 at this time.