Yeah, when Bruce Timm was doing interviews for the show he said that DC spent a lot of time and effort to build Hal back into a hero, so it wouldn't make much sense for them to turn him into a bad guy on the show. I don't understand why fans would want to see that to be honest.
Though there was a reference to it when Hal stole Larfleeze's power battery and he put on a bunch of orange rings in a callback to his rampage in Emerald Twilight, but of course he managed to fight off the influence. Who knows, if the show wasn't canceled and they decided to bring in Kyle down the line, I could probably see them do an adaptation of ET but they would've likely made it clear from the start that Hal didn't actually turn bad and Sinestro just released Parallax from the central power battery and directed him towards Hal.