UPDATE #1: I talked to another industry FOBOF who told me the following about the potential JUSTICE LEAGUE film that's in script stage at Warner Bros.: "It's being produced as if NOTHING else exists." Take that for what you will.
UPDATE #2: This isn't anything new per se, but it does show us all that the team behind MAN OF STEEL went into the thing with the idea that it was Superman's "Suprman Begins," if you will. Here's director Zack Synder about a year ago. The original story follows the video.
Question: Could a JUSTICE LEAGUE movie be set within it’s own continuity and universe without any tie-ins to future DC Comics-based solo films?
Rumor has it that Warner Bros. has at least considered the possibility, according to a longtime film industry insider “FOBOF.”
Remember, that JUSTICE LEAGUE: MORTAL film that was shut down (right before filming was to begin) was going to be outside of the continuities of both BATMAN BEGINS and SUPERMAN RETURNS and feature a Batman and Superman NOT played by Christian Bale and Brandon Routh respectively. Might Warner Bros. be thinking of going that route with this new, Will Beall-scripted project?
On one hand, potential solo films based on DC characters wouldn’t be beholden to a JL film -- like a sequel to MAN OF STEEL or the eventual Batman on film reboot. On the other, it might be both confusing and detrimental to have more than one live-action version of these character appearing in films virtually at the same time. Unless they’re planning on going MoCap/CGI with a JUSTICE LEAGUE movie (an idea that I actually support), then I’m not too keen on seeing SuperMEN, BatMEN or WonderWOMEN on film, UNLESS they are all QUALITY projects. Hell, it's certainly a way for fans to have their cake and eat it too.
It's going to be interesting to see what Warner Bros. does with its DC Comics properties over the next few years. Stay tuned!