I guess they're going with a new galaxy. I can appreciate it's the arguably the safest/best concept for avoiding post-trilogy lore issues and providing players with something new, but it's also a bit disappointing for me. I really just wanted them to pick/construct a canon and use the trilogy as a template to move the galaxy as we know it forward. Something about meeting new, space faring species in the Milky Way that just hadn't come in contact with Citadel space excites me a lot more than "you go to a new galaxy so there's new stuff".
Assuming it's another Galaxy in a timeline after the trilogy...
Will we still have relays, biotics, omnitools and all that stuff? I thought that was a product of Reaper-influenced technology, seems a bit weird if it's pervasive in another galaxy as well.
Bioware also polled people about their feelings for N7, so it seems there's still a link with the spec ops of the Milky Way. If the hero character hails from our galaxy, lore issues will be unavoidable (is he/she synthesised, why not call Shepard-controlled Reapers to solve the problem, etc.)