Microsoft released a public invitation for other consoles to join them in cross-play back in the beginning of March. It was an invitation that was more or less aimed at Sony and the PlayStation 4.
Sony didn't really accept or decline the invitation, when asked about it Sony essentially offered a shrug – they didn't even say maybe.
ID@Xbox Europe boss Agostino Simonetta has revealed that Microsoft is 'ready' for cross-platform play, they are just waiting on other developers to join in.
"Any title that wants to update their game to include cross-network play, any title that wants to launch soon and take advantage of that, we are ready," Simonetta told Eurogamer (via GameSpot).
When asked specifically on cross-play between the Xbox One and PlayStation 4, Simonetta reiterated:
"We can only say: we're ready. We've done our bit and we welcome anyone who wants to take part."
It's almost as though Microsoft knows Sony will never accept the offer, but they keep prodding them anyway.