There's one thing that is consistent about rumors: they constantly change. Allegedly the new 4-inch iPhone 5se (or whatever it's going to be called) and the smaller iPad Pro (née iPad Air 3) were to be announced during a media event on March 15th. Now the rumor mill has ground up its sources and come up with a new date range: the week of March 21st.
If I were a betting man, I'd say that means that they'll do the event either on Tuesday, March 22 or Wednesday, March 23, with deliveries of the new products beginning on Friday, March 25. While we don't know the details yet, we'll certainly let you know as soon as we hear a firm date and time for the event.