Cross network play has always been a possibility if anyone reads between PC , Xbox, and PS4. the main roadblock has always been Sony. As they initially stated back around 2016 towards Microsoft that they would be receptive of this idea. Then things changed. You can read some of these older articles between MS, Sony and cross network play.
As a current thing Minecraft has made huge advances in getting Sony to accept the idea. Yes even the article says it could be denied later. But as of right now both sides are in good talks for it.
So don’t see it so much as a legal issue (ie platforms just being incapable for legal reasons outright). Over just getting Sony to be happy with the idea. And if more developers ask for it, it may help that push.
From all the things I’ve read Microsoft has never been against the idea. If anything its made even open attempts toward Sony in doing this. So Minecraft may soon be a fully cross networked game.
If Sony and Microsoft can get along enough to agree for cross platform play with Minecraft. There is also hope that GoW can do the very same. Though at this time it may just be harder for them. So waiting a bit and seeing how the above pans out can open a huge window for developers and even GoW.
I also read in many ways Rocket League already does this. However, I’ve never played Rocket League so unsure to what extent this may be true, and how.
The thing I was thinking of which might get GoW to resist the idea. Would be the paid players, on either side or who have accounts on other platforms. IE how would a merge affect these paid players? I could see many of them being upset that they created accounts on various platforms for GoW. And now they are all linked, when all they wanted was 1 account. So even if cross networked play becomes accessible I still think it may be something GoW might not do for that reason, and others.
But who knows what the future holds <3