The two series, both written by Geoff Johns, will crossover in December.
Source: USA Today
Aquaman and Justice League will be crossing over in December during the "Throne of Atlantis" crossover. The arc was first announced yesterday after DC broke the news that Ivan Reis and Joe Prado would be joining Justice League's creative team. However, it had not been announced that the arc would crossover between the two series, both of which written by Geoff Johns.
As expected, the arc will feature Aquaman and his brother Ocean Master battling it out for the Throne of Atlantis. Interestingly, Johns states in an interview with USA Today that Ocean Master doesn't hate his brother but simply feels that he's incompetent to lead a mystical underwater nation. The arc will also feature Atlantis invading the abover-water world, marking the billionth time we've seen this story in superhero comics. It should be noted that approximately half of Justice League's issues have focused on the team fighting some otherworldly army invading the world.
Originality issues aside, one can hope that the crossover will bring Justice League up to the level of Aquaman. Johns' Aquaman series has been a solid superhero series while Justice League has been DC's equivalent to NCIS, popular with vapid plots and devoid of character development. It would be a shame to see Aquaman, which Johns will be leaving soon, begin a downward spiral due to getting mixed up in Justice League's mediocrity.