The two animated programs that currently head DC Nation appear to not have been renewed for another season. *UPDATE* Official Confirmation of Green Lantern's cancellation confirmed.
Source: Cartoon Network 2013-2014 Upfronts Press Release Lists New and Returning Network Shows
With the good, comes the bad. Today Cartoon Network revealed their 2013-2014 schedule and notably absent were Green Lantern: the Animated Series and Young Justice. Thus Cartoon Network bestowed them the same fate they gave Thundercats and Symbionic Titan. No mention at all, they're simply not renewed and thus canceled.
Alas this writing was on the wall for some time for Young Justice. First a voice actor talked about how production on the show had completely stopped once the second season was finished. Then the Young Justice tie-in comic was cancelled, with the final issue scheduled to be released next month. Finally, Mattel canceled the toy line early last year along with axing their content in the later half.
The sadder news is that Green Lantern: Animated Series was only given a single twenty-six episode season. With it's remarkable animation and intelligent writing, it's a shame the series didn't receive much fanfare which I guess is what doomed the series (ala Symbionic Titan). All that's left now is for fans to just simply wonder why and cue the petitions and outcry to these cancellations.
Now no longer speculation, Green Lantern: the Animated Series producer/co-creator Giancarlo Volpe confirms the worst via his Twitter:
This time we knew. They just didn't want us to announce it publicly until they did.
Neither Young Justice creators Brandon Vietti or Greg Weisman have yet to also confirm the news. Though it is only a matter of time before they do.