It's clear they're going to tie the story of Arknights and Endfield together in some way. The history of Terra before Endfield will probably be treated as vague, mythical, and almost ancient history to prevent massive spoilers for future Arknights 1 story events.

It's very likely Endmin and Perlica are the spiritual reincarnations of Oracle and Priestess in some way if you've read into the little details of Endfield lore.