My guess is they'll have an E3 trailer with a couple of new character entries, a brand new playable build but will probably also give us a full feature update on what's going to be in the final packaging. I'm guessing we'll some some iterative "story trailer" that'll iterate on what's been revealed so far as well as new story developments and character reveals as well as a brand new character in addition to some more existing roster. THey'll also have some kind of gameplay trailer that reveals all the extra features included in the game (CAS, guest character(s), story mode and online play).
Undoubtedly, we should see Maxi, Talim, Astaroth and Tira very soon. As well as any new playable characters.