Raven will be coming back in a better and improved version in "The 100" Season 4. She acquired ALIE abilities that she can use to bring the people to safety or even save the planet from a nuclear meltdown.
The 100 Season 4 will show the survivors dealing with last season's events' fallout but there is a new threat of a nuclear meltdown. The Earth will only be inhabitable for six months more. Clarke will save as many people as she can.