Here's how I think it will go on their way to a Justice League movie:
2013: Man of Steel
2014: Man of Steel 2
2015: Caped Crusader (Batman Reboot )
2017: Man of Steel 3
2016: Caped Crusader 2
2017: Green Lantern Reboot
2018: Caped Crusader 3
2019: Last Son of Krypton (Superman Reboot)
2022: Last Son of Krypton 2
2024: Last Son of Krypton 3
2025: The Batman (Batman reboot again because it will be about time for a new one)
2027: The Batman 2
2029: Green Lantern 2nd Reboot (because the last one failed as well)
2030: The Batman 3
Now you might notice there's no actual Justice League movie in this schedule, but that's just a matter of actually co-ordinating it so that you don't get a Superman or Batman on their way out while a new Superman or Batman is coming in. If they can manage those characters on film at both the same time, then they might be able to put together a World's Finest movie.
Also, you'll notice there are barely any other DC heroes, but that's just because WB will be trying to concentrate their efforts on their two biggest heroes.
It's a tough job this movie business at WB.