Director Ridley Scott has confirmed that yes, Prometheus 2 is still happening - and he is already working on it.
Den of Geek reports that the Alien director is pressing ahead with the unwanted sequel after finishing up on The Martian, which is due out this Autumn and does actually look really good:
Apparently Scott is currently in the process of location scouting for Prometheus 2, with him set to Direct when the film goes into production early next year. So despite the first Prometheus film being a massive stinker, clearly the executives still thinks there is an audience for it and despite everyone's completely rational reservations, the film will be getting made.
The first film, which was released in 2012, was of course a prequel to 1979's Alien and despite mining great cinematic heritage, raised more incredulous questions than it answered, as this 'review' from Red Letter Media aptly demonstrates: