DC Nation was at San Diego Comic-Con 2012, where many details about the upcoming episodes of Young Justice: Invasion were revealed, as well as the release of a new trailer.

Details released include some major spoilers, so read on at your own risk.

• Deathstroke, also known as Slade in the 2005 Teen Titans series, will join the cast.
• Artemis will become his apprentice under the alias of Tigress, and will fight Nightwing at some point.
• Static will join the cast of young heroes.
• The Partner will be revealed to be a Reach agent, who in the comics are an enemy of Blue Beetle.
• A three-eyed creature speculated to be Despero will appear.
• Tula will make an appearance in the series, though it is unknown whether her scenes take place in 2016 or an earlier point in time.
• Lex Luthor and Mercy will also appear.
• The stolen children will be given superpowers.
• The Hall of Justice will be attacked by several tanks.
• We will see Tim Drake in civilian clothing.
• Zatanna will return.

For anyone interested, I've uploaded a series of screenshots to Photobucket. And again, none are permitted on-wiki, only for a closer viewing seeing as the trailer cuts between scenes very quickly.