As for Waterston’s hesitance to confirm such details, it’s likely both Fox and Scott hope to keep spoilers under wraps either to allow fans to go into Alien: Covenant with fresh eyes, or because there may be another film or two before the prequel series directly connects to Alien. Scott previously revealed he has plans for a third and potentially fourth film in the Alien prequel series, with the final prequel tying directly into the 1979 movie.
Aside from these castings – both confirmed and not – and rumors, few details have emerged about how Alien: Covenant specifically connects to Prometheus and the original Alien film.
Plus, Prometheus co-stars Noomi Rapace and Guy Pearce have been rumored to appear in Covenant as Dr. Elizabeth Shaw and Peter Weyland, respectively.
As Waterston mentions, Michael Fassbender will appear in Alien: Covenant as a new synthetic named Walter in addition to reprising his role as the Prometheus android David.