I'm guessing that we aren't going to get a lot - James Gunn became the co-chairperson of DC's film division in October, which doesn't seem that long ago.
My guesses would be Superman (we already know that's in the planning stages), Green Lantern (it seems weird that the DCEU went roughly a decade while barely even referencing the Green Lantern Corps, let alone any specific Green Lantern), a series of some kind (not sure if it would be Peacemaker season 2 or something new), and maybe an announcement that Blue Beetle will be part of this reboot universe. (going by the cast list on Wikipedia, it seems disconnected from everything else in the current DCEU)
Even then, the announcement of two movies, a miniseries/new season of a TV show, and a retooling of a movie that we already know about already feels like a lot to me.
I'd love to see a relatively lesser-known character get a movie, like Zatanna or Plastic Man, or for a Gotham City Sirens movie to be announced (whether Margot Robbie stars or directs/produces it, I'd be fine with either - I figure this is going to be like the James Bond reboot, where some actors are carried over like how Judi Dench stayed as M), but those feel like they'd be saved for later down the line, not in the initial announcement. (I figure the initial announcement will be focused on safer picks)