Next game should start around 2960 (ME3 was 2186, Andromeda 2819). By that time, those in Andromeda can get comfortable, find a way to reliably connect to Earth, and tie the two galaxies together.
This does mean almost no returning characters from ME3 (Liara and Grunt would be the only ones who could realistically be alive for that sizable gap), but I'm totally cool with that.
But it also means every species in Andromeda AND the Milky Way. And plenty of excuses for a war...