It's worth noting OP that many in here are major advocates of the Ark theory and they believe it to be true. Thus, regardless of what you say, they will support this move away from the Milky Way even if the Ark theory, in its most basic understanding, is not practical nor feasible with what we know about the MEU.
Even though it has been established long ago that only 1% of the Milky Way has been discovered and there are billions of stars that have never been explored, these supporters of the Ark theory would rather reboot and start over with a blank slate because BioWare "wrote themselves into a corner" apparently.
Inevitably, there is no means of compromise. Mass Effect up to this point has never been about intergalactic travel or exploring the universe. It has been about the civilizations in the Milky Way that are known. I'm more inclined to believe it's far more likely we will be exploring a new region of the Milky Way rather than going to an entirely new galaxy. The rumor/survey is hardly credible and the Ark theory fails to actually explain or address anything without major assumptions and leaps in logic.
The only entity who will be able to come up with any sensible argument for why going to Andromeda, or wherever, makes "sense" will be BioWare. We'll see soon enough just how "true" these rumors are with E3 rapidly approaching. I can assure you the likelihood of the setting taking place in more than one galaxy is highly unlikely.