It's the Batman Universe and there is nothing extended about it ..
But hopefully that will change.
Give them 20 years.

with Sirens.. they can go deeper into the characters if they choose to.. the problem will be, are they going to do more than use the women as eye candy?
The WB has a golden opportunity to really make something special with Harley,Ivy,Catwoman etc if they choose to. show them at their best (when they are being flat out evil).
Maybe the Wonder Woman movie (if it's good & succeeds) will give them the blueprint on how to make Sirens good.
IMDB taught me: cynicism is praised. optimism must be stamped out wherever it can be found.

What concerns me with this Sirens project is that they could not even fill the Suicide Squad with interesting characters, Harley Quinn was probably the most interesting but even she was very lightweight and only really popular as eye candy her actual character was not interesting in this actual movie but I do think that she could have had a lot more potential. Deadshot was the only other character to really stand out but that was because of the actor and not the actual character who was really generic. The others were just filler I felt so if they can not come up with a roster of interesting characters when they do something like SS where they can use both male and female what chance do they have with just female characters?
To make a great film you need three things - the script, the script and the script -Alfred Hitchcock

Aquaman is filming in Australia next year, they just cast the character of Orm. Cyborg is still slated for 2020.
as for Sirens i think that'll happen after the current slate or be an offshoot of the solo Bat movie. I do agree that Deadshot doesn't really need his own movie.
I hope they give some news on The Flash soon. so far all we know is that they've cast Barry Allen,Iris West & Henry Allen.. still don't have a director since Rick left.
there are a handful that the WB doesn't seem to know what to do with Green Lantern,Shazam and The Flash.
IMDB taught me: cynicism is praised. optimism must be stamped out wherever it can be found.

Marvel/Disney have proven this by having big hits with the completely unknown, to non comic book reading movie goers, GotG, Ant-Man and Dr. Strange.
Yes and this is what WB should be doing but they wont because they're afraid to lose money especially after Green Lantern 2011..
Batman is DC's biggest winner, I get it but investing on him drags everything else from shining.

WB will jam Batman into everything they can because Batman sells merchandise to the general fans/public and that is the only real concern of WB. If they'd grow a set and do several Batman
and
Superman free movies I think it'd do their film universe a world of good. You could make any number of Flash movies without Bats/Supes even being mentioned and they'd be cool if you did them right. They could fix Green Lantern and make him cool as well and would have no need for Superman or Batman participation. Marvel/Disney have proven this by having big hits with the completely unknown, to non comic book reading movie goers, GotG, Ant-Man and Dr. Strange. The problem is they, WB, really only care about maxing merchandise sales so they are going to keep cramming their two biggies into everything so the names Bats/Supes can carry their action figure sales.

I'd really be fine if Cyborg or Aquaman never happen. Unless Momoa really wins me over in JL I wasn't thrilled about the casting or the look and I've never been too interested in Cyborg. The Flash keeps going through directors so I'm not sure what there is to be said yet about it. I'm not too interested in a Deadshot solo movie either but I love the idea of a Gotham City Sirens movie.