https://www.cnet.com/news/sony-ps4-gets-fortnite-cross-play/

For 24 years, we have strived to deliver the best gaming experience to our fans by providing a uniquely PlayStation perspective. Today, the communities around some games have evolved to the point where cross-platform experiences add significant value to players. In recognition of this, we have completed a thorough analysis of the business mechanics required to ensure that the PlayStation experience for our users remains intact today, and in the future, as we look to open up the platform.

This represents a major policy change for SIE, and we are now in the planning process across the organization to support this change. We will update the community once we have more details to share, including more specifics regarding the beta timeframe, and what this means for other titles going forward.