I haven’t seen definite words one way or another. We have seen dinosaurs that would have different needs in the same paddock multiple times in the previews that look happy. Further, from what the devs have said the dinosaurs' need fulfillment is dictated by territory, not what is inside the fence line. So, I would imagine that if there was something they had to stay away from it would just mean their territory could not incorporate that area of the paddock. Also, devs have said that they are aiming for more complex/interesting enclosure mechanics so it might be more complicated to put dinosaurs together, but definitely able to. I believe they said in one of the info releases that you can even put dinosaurs that will normally not cohabitate together if you build the enclosure correctly. If anything, this makes me think we will have more combination options not less.
What I'm guessing is that if the enclosure is large enough and you have the food and water separated enough, then competitor species can make their territories without overlapping and remain peaceful. And if you have another species that gets along with both, you can put their resources wherever and they'll be fine. As an example, you put one watering hole down on opposite sides of the enclosure, Steggy food around one and Trike food around the other, and they'll establish their territories and remain there since it's the only place with what they need. Then you add Brachiosaurus, put some of their food by each pond, and they'll wander back and forth with no problem between them and the other two.
However, I do have one question. Since it appears the social population limit was removed, does this really mean we can put, say, twenty Triceratops together without them fighting? Because that's pretty meh. JP lore states that any more than six in a herd and they'll death duel each other, something the first game adhered to. It would have been better to have it so that, working with the territory system, if you put more than six Trikes in an enclosure and you provide more than one pond and foliage location, the extra Trikes would form a second herd around the second pond, so twelve Trikes in the pen, they split into two herds of six and establish their territories. It's also a meh idea regarding theropods, since most of the large ones weren't social and having several rexes in one enclosure doesn't feel right, to say nothing of the Indominus rex and Indoraptor with their murderous desires.