I’m not sure how an Alien TV series would work. I suppose it depends where you put it on the timeline. After Aliens, like the Dark Horse Comics series spanning thirty years, where the threat is known but still dangerous? In with the recent prequels keeping it secret? Or are we talking reboot?
I’ve run and played a few Alien(s) one-shots (never using the official Aliens RPG) and they’ve all been one-shots, though they didn’t all end with everybody dead.