My earlier suspicions were correct: IMAX has scrapped the 3D release of "Justice League." Early posters for the movie proudly touted the movie as being an IMAX 3D release...only to slowly get away from that claim and just being advertised as being "in IMAX." Though this may not be the final listing, so far...
...NO ticket pre-orders are selling any showings of the movie that are in 3D, which means its pretty unlikely there will be any when the time comes! This contributes more to the notion that IMAX is getting out of the 3D game, but it should be noted this seems like an exception to the rule rather than the norm. Right now "Thor: Ragnorok" is playing in IMAX theaters with 2D and 3D showings being split pretty much down the middle. "Geostorm" was shown completely in 3D regardless where it played. "Star Wars: The Last Jedi" will have some 2D showings, however the vast majority will be in 3D. Which means, since making the original announcement, "Justice League" will be only the SECOND release to ditch 3D from a movie that has a 3D version available (the first being "Blade Runner 2049" of course).
What is odd about this movie is that originally it was being directed by Zach Snyder, who stepped away from the project after his daughter tragically committed suicide (and my thoughts and prayers are still with him). Joss Whedon was brought in to finish the film, but in the process has apparently restructured the film, has written lots of new scenes, cut Lex Luthor from the film, and has made the movie more humorous and colorful. From many accounts, it is now more Whedon's film than Snyder's. Why do I mention this? Because while Snyder was making a movie that he knew was going to be converted to 3D, Whedon might not have been. Granted, he HAS directed 3D films before ("The Avengers" and "The Avengers: Age of Ultron"), but he might have been too busy fixing the movie to worry about how it was going to be presented in 3D! Warner Bros. does have a conversion in the can, but it might not compliment the scenes Whedon has directed, and it's entirely possible the director told IMAX not to bother projecting the it that was as a result.
Or, maybe, "Thor: Ragnorok" really did sell more 2D tickets than 3D. Look, it's entirely possible. I personally think that if you did that you made a mistake because the 3D in that movie was extremely well done and immersive, and it reminded me why I loved 3D movies so much. There's no solid numbers on that though, so...I can't comment on it. Right now I'm thinking the lack of an IMAX 3D release has more to do with changing directors than anything. However, I will do my due diligence and see the movie in both formats and give you my two cents on them, and which one you should see.
You're absolutely right about Whedon. I know someone that works on IMAX and whedon said the 3D conversion was not good and it would've taken more months to properly release this in 3D, so Whedon told IMAX not to release it in 3D.