It is quite possible that Harley Quinn was a fan favorite when "Suicide Squad" was released. It is no doubt that her high ratings encouraged the directors to create a spin off and make a movie where Harley is the main focus.

AV Club created an entire article based on this phenomenon. They mentioned Harley's fame regarding how she was perhaps the most used costume in Halloween. There are also many merchandise being made because of the amazing actress who managed to play off the character incredibly. 

However, recent news suggests that the movie has a very high chance of being a Birds of Prey movie. 

Birds of Prey, according to Cinema Blend, is another group adventure in the DC universe. True to its name, it features an all female cast of various heroes including Black Canary, the Oracle, Huntress, and now Harley Quinn. 

This focuses on the female side and if this does become true then not only will this movie expand Gotham in the cinema industry, but it will also expand the female side of DC movies and introduce various new characters such as Black Canary.

As of right now the only screen time Black Canary received was in the TV show "Arrow". If she is reintroduced in "Birds of Prey" then she could be a new person. This also means that fans may see a new Oliver Queen (Green Arrow). 

It is good that DC is focusing on group character activities. Considering how Marvel is excelling in the department with "Avengers", "Civil War", and "Guardians of the Galaxy". 

It is time that DC stepped up to the plate and do the same. The upcoming years are quite an exciting series of upcoming movies all with unique stories and interesting plot points. Birds of Prey will be one of them.