https://www.cnet.com/news/apple-next-event-is-on-march-25-teasing-a-show-time-announcement/

In recent months, Apple has made a string of content deals, including those tied to the creation of shows. Some of these shows, such as Carpool Karaoke, are already available through Apple Music. Others that aren't yet available appear to be coming from deals Apple has made with stars such as Oprah Winfrey, Reese Witherspoon, M. Night Shyamalan and Steven Spielberg.

There are also rumblings that Apple may be set to reveal a news service, which would also line up with its acquisition of news subscription aggregator Texture. So that's another possibility for the March 25 event.