I haven't read this whole thread, but there is something I'd like to respond to.
Yes, only 1% of the Milky Way had been explored, but practically all that could be explored with the limitations of the Relay Network has been.
The Relays allowed us to travel across the galaxy quickly, but it also made it impossible for the races to leave the relays or try going too far from them because their technology, like all the cycles before us, followed the technological patterns the Reapers deigned us to follow.
And no where in the galaxy has NOT been affected by the ending choice as the Relays essentially transformed the entire galaxy thanks to the Crucible. All of it, not just 1%.
As for going to Andromeda, I can see a group of various races from the Milky Way leaving on an exploration, or a last ditch survival effort before ME3's ending took place, like the Asari Councilor saying that there were options that must be taken after the fall of Thessia. Where the humans, asari, Krogan and such enter the Ark Ship fully expecting to be the last of their kind, never to return, and take a prototype ship meant to leave the Milky Way behind and set up roots elsewhere, so even if the war against the Reapers is lost, their races will survive.
I'm not going to bash a new team or go on and on about how horrible it'll be because it's a departure from a lot of what we've known. When the game comes out, I will take it on its own merits.