Oh well at least according to Joss Whedon it ain't happening, contrary to the signing rumors that have been appearing in the British press. However, I do know that there has been some activity in trying to find a new director for the series, and perhaps they're (FOX) waiting to find a director before going out to writers...
Harry, here's some depressing news for all the Alien 5 fans out there: At the San Diego Comicon this weekend Alien Resurrection screenwriter Joss Whedon was asked, "Are you, or is anyone, working on a script for Alien 5?" Joss replied: "Uhh, that's a big nooo. Did you see Alien 4?" This drew huge laughs from the audience to which he hid his head in his hands and was jokingly consoled by Buffy the Vampire Slayer cast members.
What a bummer, with the right story this series could still have some life left in it. If you use this, you can call me Alien Fan.
