I received an IM from a friend who works for a major visual effects company that is often times brings in outsourced work from major film companies to help ease the work of filmakers. He's currently signed enough NDAs to keep him quiet for life, but he was willing to share what he's seen.
From what he's told me, he's seen different levels of effects for different scenes. Each vary, from either slight variations, to some that actually change the outcome of the film outright. In his words, "There's a lot here, and I feel sorry for Nolan, because there's a lot of good stuff here"
Without going into too much detail, he told me with most versions of the ending, it starts with Bane activating the machine that we've all seen in countless spy photos, and of course we saw the effects of that in the trailer. He says that Bane is actually trying to amplify the machine, and that there are safeguards in place that prevent even more widespread destruction. By the end of the film, Bane has succeeded in removing those safeguards and is capable of leveling Gotham with his machine.
Some people are saying that Bane and Talia join forces half way through the film, but the impression that my friend got was that Bane (being a mercenary) is actually contracted by the League of Shadows.
So here's where things deviate between endings:
I) Bane activates the machine, and while Bruce attempts to stop it, he doesn't reach the machine in time. Final shot is of Gotham literally in shambles, Bane has been apprehended, Talia escapes. Gordon and Bruce have dialogue similar to the first two films, but instead of either of them thanking eachother, they start working to rebuild Gotham; and the city of Gotham (as well as the Police) accept Batman as a force for good.
II) Bane is defeated, but the device is active and with little time to spare. Bruce tries to call in The Bat (the flying machine) remotely as he tries to take the device as far out as possible. sadly, the signal emanating from the device scrambles the remote control and Bruce has to manually fly the device out to sea. A large explosion takes place and it's assumed that Batman died in the explosion. People have been trying to figure out who JGL is playing, and rumor has it...he's playing John Blake. He helps out Bruce during the course of the film, and evnetually takes over the cowl. End of the film echoes the ending of the first, but with JGL wearing a newer Batsuit (Described as very Batman Beyond-esque). This is also supposed to mirror the words said by Ras Al Ghul in Begins where he mentions how Batman can be a symbol, more then just a man. Despite the death of Bruce, Batman lives on.
My friend mentioned that he sees space for what he would describe as a post credit sequence for this ending. I asked if he knew who was in it, but he told me that nobody has seen this, and he doubts that unless this ending is chossen, then no one will know.
III) Personally, this last set doesn't sound very plausible to me. I guess you could say the same about all of these, but this one wouldn't surprise me as a quick toss aside.
In this version, it's Catwoman Vs. Talia and Batman Vs. Bane. Catwoman and Batman succeed. In this version, the device is set to detonate but in a very-anti-climatic way, it just fizzles out. From what I hear, this is a VERY simple ending, one without too much of a punch or some thematic elements. It doesn't sound like this would be a horrible ending, but it's just way too safe.
So there you have it. My friend has said that it's very unlikely that we'll see all the endings aside from the DVD/Blu-Ray release but he does mention that the choice needs to be made soon; but with so much pressure on closing off the Nolan trilogy well, Nolan is being very meticulous about the choice made. I really do think that all of the endings will be on the Home Release circut, be a great way to boost sales when it hits. I trust my friend, and have no reason to doubt this, but until July 20th; I guess it'll remain all a rumor.