Marvel will be at D23 as other have said.
For DC, here's about what I expect.
BvS: New shakey cam footage courtesy of a
WB employee really brave fan. I expect this to comprise the bulk of whatever presentation WB have planned for their DC slate, so extended questioning and such with the entire cast and Synder. Some kind of reveal. Either the physical threat or Luthor's Power Armor (assuming the rumors about it being in are true).
Suicide Squad: A bit of questioning for the cast members who join the panel. Maybe some shakey footage of an early cut of the Joker/Harley scene we saw, but that's a long shot.
Wonder Woman: If we see anything at all, it'll be a logo a maybe an announcement of who's playing Steve Trevor.
Justice League: If we see anything at all, it'll be a logo and maybe concept art of the entire League.
Other Solo Films: Same deal. Logos if we see anything. Maybe we'll get a picture of Rock as Black Adam. Maybe. Might get some release dates.
Vertigo: Probably nothing, unless JGL da gawd shocks us all with Sandman.
TV: Trailers for the new seasons of Flash, Arrow, and Gotham. More info on Supergirl and Lucifer. More info on one or two other projects they've had cooking.