As always, take stuff like this with a grain or two of salt.
CBR is reporting that Swamp Thing was planned for a three-season arc and that there was even talk of a Justice League Dark spinoff.
Now this source that says this stuff was ‘discussed on set’ so it could have been cast or crew members who were just hoping/imagining/speculating themselves and it was overheard. So there’s no concrete evidence. But it’s the internet, so…
https://www.cbr.com/swamp-thing-three-season-arc-justice-league-dark/
But if this were true? Oy, what a way to twist the dagger… 