The DC Universe Online site has great news for all players with the arrival of the Earth 3 Episode. In this new episode, players will have to work both sides of the aisle with Justice League and Lex Luthor to combat a new threat to Earth. There are new missions "in an open world environment" as well as a new Duo (and an Elite version), a new Operation and two new Raids.
In addition, for a short time, players at level 10+ can take part in all aspects of Earth 3. Event versions of Earth 3 can be found in the Events tab.
In addition, Superman's model has gotten a big update this patch. "Superman is now new and improved for not only Earth 3, but all prior DCUO content as well (with the exception of Legends Superman, who has not changed)".
You can read the full update notes on the DC Universe Online forum.