I would be down for crossplay if they wanted to add it in to some games, but it's not something I'm foaming at the mouth to get. Most Switch crossplay wouldn't mean anything to me since MHW is too much for it, though it'd be nice to play Dark Souls Remastered with my Switch friends from my couch.
So that brings me to PC and Xbox. Crossplay with PC is, in my opinion, significantly more important than crossplay with Xbox. In fact, I'd say Sony should talk to Valve again about getting some kind of compatibility with Steam. Xbox is less important, though, especially for me. Most of the games I personally enjoy aren't super popular on Xbox and have rather small communities. Outside of that, the XB1 community is just smaller as a whole, not 80m strong like PS4 or obscenely strong like Steam.
If Sony can make it work with Xbox, great. But Steam should have priority.
The thing is Sony already has cross play with PC as well. Final Fantasy XIV, Fortnite, Warframe, etc already do this. The only reason it looks like the X1 has more PC crossplay is because their "exclusives" have it while the PS4's exclusives are actually exclusive to the console. Well that and the fact that Sony has a bigger focus on single player games.
Most 3rd party games lack crossplay altogether. I do not think PC crossplay will ever be an issue for any console maker. They just do not want to share with their direct competitors. It is a shame because I feel like ONE company will always be against it.
During the PS360 days, MS blocked cross play and Sony was for it. Now that the tables have turned, Sony is the one blocking us. If things flipped again, MS could very well go back and say no.
I feel like crossplay will remain just outside of our reach on consoles until there are three consoles powerful enough to support it. As it stands now, Nintendo will not keep up in power next gen so Sony has zero reason to fold aside from just being nice.
This is the sad truth.