What's up with 'Gotham City Sirens,' 'Nightwing' and 'Black Adam' at DC?

When Warner Brosannounced its slate of nine upcoming films at Comic-Con on Saturday, we couldn't help but notice a few big omissions.
Embedded within the sizzle reel were nine titles and logos, most of which we knew were coming, some of which (like Wonder Woman II) are now officially official. Make no mistake: Nine is a lot of movies to have lined up.
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But what has become of Gotham City Sirens, the Harley Quinn-led female villain team-up