Update 2:45: We received word back from Warner Bros Animation, who made this 100% official - yes, Young Justice will be on an episode of Teen Titans GO! this year. While they couldn't reveal too much just yet, we did get the official logline (description) of the episode, and it sounds like they're directly addressing the considerable difference in tone between the two series.
"After being scolded by the superhero team from Young Justice for their silliness and hijinks, the Titans decide to get more serious about superheroing."
Original Story: Young Justice is still fresh in fans’ minds - with a large and eclectic line-up, unique takes on the young heroes of the DCU, and story lines just complex enough to keep older viewers involved, the series was praised almost universally - but was then canceled after two seasons, themselves shown via an erratic (to say the least) schedule.
While there’s no return of the series or any kind of movie closure planned, the characters will at least hit TV once more, in a special crossover episode of Teen Titans GO!. The series has much more of a comedy bent than the action-drama Young Justice did, but fans should be happy just to see some of their favorite characters on screen once more. No details have been given yet, such as what characters, which episode, whether it will be just a 15 minute segment or a full half hour, but we have reached out to Warner Bros for more.
Brandon Vietti, half of the Young Justice team, did confirm that he and Greg Weismann are not involved in the crossover episode, “but it’s gonna be fun none the less!” he assured fans on twitter. More on this as we get confirmation from Warner Bros.