Microsoft have said they are ready to talk to developers who want to feature crossplay, citing Nintendo and Valve especially. There are of course games already that do this, but this is now being extended to anyone who wants it. It's funny watching MS who were sort of against this last-gen come out supporting it more and it is Sony who are the 'bad guy' now, because of their attitude towards it.
It would be excellent for this to happen in my opinion, certain games are set for it - sports and racing titles especially.
Microsofts open invitation to Valve, Nintendo and others to join Xbox One and PC crossplay | VG247