It was Epic and Fortnite that got to be the first to offer truly cross network multiplayer, as Sony relented and allowed them to do so. Now Epic are offering up the infrastructure they built to support this in a new SDK for other developers.
The Online Services SDK will feature “cross-platform login, friends, presence, profile, and entitlements” as far as each platform allows it, and will be rolled out through 2019, with integration for both Unreal Engine and Unity.
Starting in Q2 there will be cross-platform data storage and cloud-saved games, while cross-platform achievements and trophies, voice communications and a PC/Mac overlay will come in Q3, and finally cross-platform parties and matchmaking toward the end of the year.
Epic also plan to support user-generated content, more social features, anti-cheat and more after these have been completed.
Cross-network play isn’t as simple as flipping a switch or writing a few lines of code, and it makes sense that Epic are pushing to turn their expertise into a new product. Hopefully some other alternatives appear as well, but this could take a lot of pain out for smaller teams that want to ensure as much longevity for their multiplayer games as possible.