[En Sabah Nerd]

Yes, I'd say there is a sci-fi/horror (or horror/sci-fi if you like) hybrid genre. If we look at Alien as an example, it has a sci-fi setting and elements but still heavily features horror aspects like the monster stalking and killing people. One distinction is the level of actual explanation given, the more they get into discussing the "science" the more it becomes science fiction. Alien and The Thing don't really tell us crap about the monsters' origin or reason-for-being, and that makes them more horror but you can't deny the sci-fi elements weaved into it. Think of it like horror/comedy movies, Evil Dead 2 is more horror themed but still comedy while Shaun of the Dead is more comedy yet still has some horror bits.

Predator isn't really a horror. It's an action/sci-fi/thriller mix, obviously action but undeniably uses sci-fi parts with thriller considering the build up to the alien's reveal and many of its kills are thriller style scenes. The franchise has been tied to the Alien franchise, so I get why they're usually thrown around together. Aliens was also more action than horror, but there are still horror moments throughout.