Well, if you can get Justice League to work, why not lay the foundations to set up Titans? That seems to be the go forward for the WB/DC Cinematic Universe as they’ve announced a Nightwing stand alone movie with Chris McKay (The Lego Movie) attached to direct.
Nightwing is Batman’s off-sider Robin as an adult who has split from the caped & cowled hero after a dispute and become his own crime fighter. He goes on to form a group of younger superheroes called Titans (aka a younger version of the Justice League). At the end of The Dark Knight Rises, Christopher Nolan hinted at the character when Joseph Gordon-Levitt’s ‘Robin’ character discovers the Batcave.
So, what’s on the DC movie slate thus far:
Justice League, Wonder Woman, Man of Steel 2, The Batman, Aqua Man, The Flash, Suicide Squad 2, Harley Quinn, Shazam, Nightwing, Cyborg, Black Adam, Green Lantern Corps, and Gotham City Sirens.