If the AI ever does reconnect to the Milky Way...

As themikefest has said though, it is possible for Liara to have died right at the end of ME3 and/or everyone to have died if the Refuse ending was chosen and the harvest continued.  People accuse Bioware of wanting to avoid dealing with the endings... but I think what they really want to avoid is declaring a singular canon ending.  That means that any communication to the Milky Way would have to be done in such a vague way to allow for the possibility of any of the endings to have taken place (rendering it likely "unsatisfying" for the bulk of players who are still insisting on being in the Milky Way to force Bioware to "deal with" the endings) or to "completely and finally end the ME:A saga with a return to the Milky Way" in such a manner that either, again, the state of the Milky Way and the old characters remains unknown or the player simply selects / reselects an option to declare what state the Milky Way would be in at that point.  With future improvements to gaming technology, it may be feasible for Bioware to manage a continued game that starts with such variation in the state of the setting... but I think it's highly unlikely and probably not going to be worth their while, financially, to attempt it.

Historically, part of the experience of taking the risk of migrating to a "New World" was learning to deal with the yearning to return to the "Old World" and, for many, accepting that such a return was never going to be possible.  For me, the possibility of never being able to return to the Milky Way actually makes the potential characterizations in ME:A more "real."  In addition, some of my ancestors that came to the "New World" were blatantly lied to about what they could expect to find here... so the idea that the AI might resort to lying to their participants is an intriguing story element for me.