We don’t know why Shane Black and company didn’t go with the Ripley ending, as it would have been cool and still set up intriguing possibilities for humanity’s hope in a potential sequel. However, it also might have been considered a bit too convoluted considering that Ripley is from over 100 years in the future, so to introduce a time travel head scratcher at the end might have been a bridge too far.
Article source: https://www.cinemablend.com/news/2464287/the-predators-ending-could-have-included-aliens-ripley