Going to the Milky Way in Sequels

If the colonists would ever return, something like 1200 years would've passed. Probably more. The Milky Way would be unrecognizable just because of new technology, uplifted races, etc.

What makes it impossible is that BioWare chose Andromeda as the new setting, so that all choices by players in the original game can be canon. Returning to the Milky Way can only be done by making choices canon. If BioWare would consider this, then there would be no reason in the first place to go to Andromeda.

We will never go back to the Milky Way. It's a one way trip.

If the series is successful enough to keep producing games then I could see us return to the milky way but not for 2 or 3 games down the road.

It depends on MEA. If for some reason it does poorly, I don't believe it will, what will EA do? I'm sure they've already gone over scenarios if that were to happen. I would not be surprised if they have another game take place in the Milky Way. I even go as far as to say they may even bring Shepard back. I would have no problem with that.

I can see a potential return to the old MEU setting if this doesn't work out, but a rehash of Shepard seems like the least likely scenario to me.

Probably not gonna happen, I think.

They'll want to focus on building the Andromeda setting and new stories there, not shlepping back to the MW to open old wounds.

Both can be dead depending on the playthrough

It may happen (with inevitable canon-choice/reboot angle) but not for another 2-3 games, as said already. ME3 ending was too much of a shitstorm to follow up with a reboot or homogenized/canonized-choice sequel directly. Time has to pass, if there's ever enough time for fanbase to trully get over it. Andromeda is the solution for the longer time being.

Not to mention purely developement point of view. They'll want to reuse current Andromeda-specific assets they've created for the whole generation (whether its 2, 3 or 4 more games). Goes for new species models, architecture, lots of art etc. They won't be remeaking that from scratch every game.

Andromeda is not a solution, it is the antithesis of a solution. It creates way more problems than it solves. An actual solution would be to clean up the ME3 ending mess and eliminate the need for Andromeda in the first place. Andromeda is just BioWare's way to continue milking their fans without having to owe up to their past mistakes.

For the record, the ending hatred came into existence because the ending ruined the Milky Way, and the reason the ending hatred is still burning hot as a sun is that the Milky Way remains ruined almost-five-years later because BioWare refused to un-ruin them, going as far as moving the entire franchise to a new galaxy fans don't give even half a shit for only so they can continue to milk their fans without having to un-ruin the Milky Way.

People should stop buying into and parroting BioWare's "player choice is sacred" BS, especially since the previous games made it clear BioWare doesn't give and never gave two cents about player choice. A lot of people chose an all-human council in ME1. It was retconned in ME2. Did anyone give a shit? Nope. A lot of people chose to save the Collector Base, thinking it would have far-reaching consequences and allow the players to continue working with Cerberus. What happened? It gave 10 more War Assets and didn't even remotely affect Shepard's relationship with Cerberus. Did people give a shit? Nope. Not even a tenth of one percent of a shit.

The endings aren't some golden geese worshipped by BioWare fans. The only people who actually, genuinely care about them are the people working at BioWare, the same people who made them and in their ignorance believed they were good. And I seriously doubt even a single fan would give even the tiniest elementary particle of a fuck if declaring the endings non-canon - including their favorite one, if they have one - meant BioWare could continue to make games set in the Milky Way.

I agree with the likelihood being higher that Milky Way species could be at Andromeda before the Arks arrive there, but it is actually much worse than that. One could get to Andromeda from here in around 200 years time at speeds close to, but still slower than lightspeed (I think for ME:A the rumored number is 600 years). But time is not invariant (light speed is), so those years would be the subjective time that the travelers experience. Due to time dilation from relativity, this would be equivalent to more than 2 million years back at the Milky Way point of origin.

So depending how much technological advancement or "space magic" happens on such timescales, it might be more likely that the ancient remnants are actually the remains of the Milky Way species that set out to Andromeda eons after the Ark explorers themselves after discovering some way to circumvent general relativity via instant wormhole travel or stuff like that. So I don´t think that they will write it in a way that we will return to the Milky Way and see characters from the trilogy there, but maybe our far-future descendants will already be at Andromeda. That may actually offer some interesting story options .      

Relativity/time-dilation isn't a factor with Mass Effect's FTL, though, and we've no reason to believe the Arks will be travelling at sublight for the journey to Andromeda.

As others said, I doubt it'll happen. They moved to Andromeda to avoid making things canon. If we ever return, they would need to do that, since there's too much difference between endings.

The wait calculation does not necessarily factor in the near-apocalyptic scenario presented in ME3.

Even in the best possible outcome where the Reapers are stopped and everybody lives, every single civilisation still has to rebuild after suffering a galaxy wide near-apocalyptic level event. Most of the homeworlds are in ruins, with Earth and Palaven being said to resemble Tuchanka. Everyone is limited to FTL speeds because they still need to repair the heavily damaged Mass Relays, which will take a lot of time and effort to get the Network running again, if certain Relays even can be salvaged.

Assuming that everything that can be rebuilt can be (with Synthesis/Control having Reapers to do a lot of the heavy lifting), by the time that MEA takes place, the Milky Way might only have just recovered to the state it was in prior to the Reaper invasion.