Yes, it seems that Swamp Thing has been canceled.
However, reporting suggests that it’s not because of a lack of faith in the show or in the DCU service. It’s because of a $40 million screw-up perpetrated by the North Carolina legislature.
WB agreed to shoot Swamp Thing in NC because of a huge tax break that was promised to studios who filmed there. Swamp Thing’s budget was estimated at $80 million - so just imagine what it must have been like when suddenly they got their budget cut in half! Heck, I’m surprised they were able to salvage anything, turning thirteen episodes into ten.
So of course things are being reevaluated, for both Swamp Thing and DCU. They just lost millions upon millions of dollars through no fault of their own and they’re trying to find a way forward that’ll keep everything up and running.
But if Swamp Thing continues its quality run, garnering more and more adulation, WB/DCU will eventually find a way to keep it going. It’ll take another huge initial investment, but if we the community keep calm and continue to support both the show and DCU, it’s a distinct possibility that we might get a second season some day.