The announcement will made at 1 p.m. EDT from Washington, D.C. and followed by a Q&A session.
We can only guess what the SpaceX founder has planned, but the big news comes exactly a week after SpaceX successfully launched its Dragon spacecraft on a Falcon 9 rocket to the International Space Station.
It was the first time the private space transport company launched the Falcon 9's first stage equipped with four "landing legs," as part of a test to see if the rocket can be recovered and reused. The landing legs would eventually be used to land the rocket on the ground, but the first test was done over water.
The first stage managed to make it back to Earth without burning up, and splashed down into the ocean. The last update on the first stage landing from the SpaceX website reads: "Data upload from tracking plane shows first stage landing in Atlantic was good! Flight computers continued transmitting for 8 seconds after reaching the water. Stopped when booster went horizontal. Several boats enroute through heavy seas ..."
So the announcement could be an update on that.
Here's the launch again, from the NASA Kennedy YouTube: