It's not been too long since the Minecraft debacle, where Microsoft announced cross-play with Minecraft across different platforms, with one exception - Sony's PS4, as Sony publicly admitted its refusal to allow cross-platform play.
Now, it seems Sony is at it again. The studio behind early-access game ARK: Survival Evolved, Studio Wildcard, has said that they have an internal build of ARK: Survival Evolved that has cross-play working between PS4 and Xbox One, but that it isn't available as "Sony won't allow it".
Studio Wildcard's co-founder, Jeremy Stieglitz, sent out a tweet in response to a question posed to him with playing with friends on other consoles (via Neowin), to which it was said that Sony isn't allowing cross-platform play:
We have it working internally, but currently Sony won't allow it 🙁
— Jeremy Stieglitz (@jeremystieglitz) August 18, 2017
While Sony's decision isn't set in stone, it seems that for now at least, Xbox One and PS4 players will continue to remain on their separate sides (unless, of course, you're lucky enough to own both consoles).