I want to start this off by saying that from what I can tell, it's not Hi Rez that are stopping PS4 from being able to crossplay with Xbox and PC, but it's Sony doing the blocking.

However, lately it seems that Sony are being a lot more open when it comes to crossplay games, for example the newly announced Call of Duty game will be crossplay between the 3 platforms and obviously Fortnite already is. You also have Sony working with Microsoft on from what I've seen is cloud based gaming.

I'm thinking that this, would most likely be an opportune time for Hi Rez to push Sony for crossplay for their games.