One expansion I was thinking about recently that I'd like to see at some point is a source book for all the different Alien variations we've seen throughout the comics, games, figures etc. There are so many out there beyond the ones we've seen in the movies - which mostly all have stats now between the current releases - that it'd be great to get some (and a bit more lore and artwork) for things like the Bull Alien or the King or the Queen Face Hugger.
The only downside could be that they might not be able to include the Predalien or things like the Carrier or Ravager and others that appeared in an AVP context. So that wouldn't be too great. But regardless, if it was as comprehensive as possible it would still be a really cool expansion to have, both from a gaming and a lore standpoint.