Alien: Convenant isn't out yet but director Ridley Scott is already talking about the sequel. In an interview with IGN Scott said that work on the movie is already in motion.
"We're writing [a sequel] now, as we speak. I'll be filming that within 14 months."
The interview also brings up the now canceled Alien 5 from director Neill Blomkamp and refers to the movie as Awakening.
"They wanted to do Alien, er, Awakening – Neill Blomkamp", he explained. "I said fine. I was going to be the producer. If I could have, I would have. Except I do question – why have both [Blomkamp's Alien and Scott's Alien] out there? It seems like shooting your big toe off – it doesn't make sense. But they didn't go forward with it, Fox, so I just kind of kept out of it. I mean, I'd literally ignited this thing to bring it off the ground again, because it was lying there dormant on a shelf. I had this thing to bring it back up – but here we are."
We're going to have to agree to disagree on the "shooting your big toe off" thing because there is absolutely enough room in the world for two different Alien timelines. Scott does have a standard for these movies, though, and as long as they keep meeting it he'll keep making them.
"It's good when it's good. If the sequel's good, then it's worthwhile."
As for all of the unanswered question we all have? It's being left vague on purpose.
"That's why I'm doing it, so you're asking these questions."
Alien: Covenant will be released in UK on May 12, 2017 and in the US on May 19, 2017.