There was a lot of talk of a sequel to Prometheus being in development after it's release, as the ending was a bit of cliffhanger leading to a second film. To be fair Ridley Scott and writer Jon Spaiths actually outlined two films originally, more than a year before Scott signed-on to direct. So the people involved with the original film have an idea of where the sequel is going.
During an interview with ThePlaylist actress Noomi Rapace revealed meeting and speaking with Ridley Scott recently about the sequel. She doesn't mention too much but the project is currently in script phase and the creatives are still putting together the story. Likely, referring to screenwriter Jon Spaihts and Ridley Scott as Damon Lindelof (who only added terrible rewrites) will be focusing on Tomorrowland and Star Trek 3. However, the studio hasn't announced anyone is actually writing the script. It's possible Spaihts is has been quietly re-working old Alien: Origins scripts to meet the needs of Ridley. I would assume that this script could be further along than the Blade Runner 2 script. It also sounds like Ridley Scott is keen to return as it's director.
"They're working on the script. I met Ridley in London a couple of weeks ago. I would love to work with him again and I know that he would like to do another one. It's just like we need to find the right story. I hope we will."