I read somewhere that even netflix didn't consider the audience numbers of YJ stellar enough to give a free go with more seasons, but they said they will consider coproducing or something because the fans were very supportive of the show, i for once liked the show and green lantern animated series but they decided to cancel both and they didn't truly pick up anything from de DC nation shorts aside from teen titans go.
Besides i don't know if DC Superhero Girls is successful but i've seen a heck a lot of merchanside and the animated shorts have toons of views on youtube, so yeah they still might think in selling toys instead of giving a good series first.