Information on the new cross-platform development kit that Microsoft plans to unveil was spotted on the schedule for the Game Developers Conference 2019 event by Twitter user Avers (via Windows Central). Titled "Xbox Live: Growing & Engaging Your Gaming Community Across iOS, Android, Switch, Xbox, and PC" and presented by Microsoft, the event's description touted the success of Xbox Live so far and said Microsoft plans on making the use of the service even more widespread by giving developers the tools to connect players on different devices.
"Now Xbox Live is about to get MUCH bigger," the GDC 2019 listing said. "Xbox Live is expanding from 400M gaming devices and a reach to over 68M active players to over 2B devices with the release of our new cross-platform XDK."
It continued to preview a software development kit aimed at developers which will allow them to "connect players between iOS, Android, and Switch in addition to Xbox and any game in the Microsoft Store on Windows PCs." The listing said Xbox Live users are already engaged on Microsoft's Xbox and PC platforms and listed achievements, friends lists, and clubs among other features as the perks of having Xbox Live support on non-Windows devices.
"Game services engineers looking to save time & expand their customer base by letting Microsoft managed game services handle social, communication, and multiplayer interactions across billions of screens," the event description said regarding the target audience for the event.
Microsoft has already expanded Xbox Live to some games on other platforms, so this initiative seems to be that on a much larger scale by bringing Xbox Live itself to these devices. Minecraft is one of the first games that comes to mind seeing how it's cross-platform compatible and even unlocks Xbox Live achievements for those who play it on the Nintendo Switch.
Sony has been making progress with its cross-platform plans by allowing PlayStation 4 users to play some games such as Fortnite and Rocket League with others on the Nintendo Switch and Xbox One, but that platform is noticeably absent from this GDC 2019 listing.
GDC 2019 is scheduled to start on March 18th and will be ongoing until March 22nd.