While a an earlier leak suggested Dishonored 2 would be announced at the press conference, the team showed a full trailer of what we should expect. And it was awesome.
You can play either as Corvo again or as a new assassin Emily. The new trailer shows off Emily Kaldwin–the princess orphaned in the first game–and she's a badass:
As in the first Dishonored, Harvey Smith confirmed, "You can play the entire game without killing anyone."
In the post show interviews, Smith also revealed that Emily will have a unique set of powers that won't cross over with Corvo's abilities. Something which has caused no end of challenges for his level designers. Unfortunately, he confirmed that despite these two characters, Dishonored 2 won't have co-op.
The new game will move away will from Dunwall to Karnaca, a town on the southern isle of Serkonos. It doesn't come up in the trailer but it's the island where Corvo was born. We also learned in the first Dishonored that Serkonos' ruler, duke Theodanis Abele, had two sons, one of whom was killed in Dunwall.
One last bit of Dishonored trivia, we learned in the first game that Karnaca has a special police force, the "Grand Guard". Essentially a military-run city guard, each member is picked by the duke and very highly trained.
I can't wait to learn more.