I predict the the new endings will likely be massive compromises. By which I mean that they still won't be what many people are hoping for. Even excepting that "you can't please everyone" which is quite true, BioWare cannot lose the old multi-coloured nonsense and the Ghost Child drivvel without being seen to be compromising "artistic integrity" or "original vision" or some rubbish like that and admitting that their ending(s) sucked harder than a biotic singularity before.
So new endings...there will likely remain everything up until the "ending machine", the initial videos will probably play as before, but there will be more cutscene of things happening. These things will likely include a flash of surviving squadmates/love interest, a brief shot of the Rachnii queen (if she lived), Cal'Reeger (s/p?) and other surviving NPCs with what they were up to during the battle. Maybe if we're lucky, there'll be an image of Shepard (unlikely), or the aftermath of the player's choice, in the form of a shot of various worlds and how it looks after the war.
So yeah, a big compromise. They'll extend the endings to include more shots of people and places, but in order to stay "true" to the shit endings they originally included, they'll probably keep them shit. I suspect that any hope of an actual "good" ending will be swiftly dashed.