Kevin Smith talked about this on a recent episode of Fatman Beyond, but he spoke with someone who was on the production team for JL, and that person saw Jim Lee's storyboards for all three films in the trilogy. The first was close to what we saw. Part Two was the JL taking the fight to Apokolips and it ending "like the Empire Strikes Back" with them failing. The third would have been set in the nightmare vision Batman saw in BVS as they try to save the planet. Probably not new news, but I wonder if someone will ever release those storyboards.