Here's a conspiracy for you. At the end of ME3 the Normandy crash lands on a planet that looks an awful lot like a golden world. So, what if the Normandy, and possibly some of the other warships in transit got pushed a lot further than we assumed and actually got chucked out to Andromeda, long before the Initiative arrived, although possibly in a different cluster. If this is the case we might eventually run into them later, both as the original races and possibly new ones.
Possible encounters: Matriarch Liara and her 1 or more blue Shepard babies (c'mon, whether or not Shepard dates her, given the size of her crush and the number of times she's "embraced eternity" with Shepard it's a given)😉
EDI and Joker's Cylon-race decedents, and possibly EDI😃😎
The Flitan Floghtila, a Quarian-Turian mixed race possibly started by Tali and Garrus❤️
The Sons of Vengeance, a Prothean-Human mixed race possibly mothered by Shepard if she survives (I'm a romantic at heart, so if the Crucible-Relay interaction sends ships to Andromeda it might as well send the contents of the Citadel or the Citadel itself as well, so Shepard can be reunited with their LI if surviving)👿:eahigh_file:
Warlord Grunt and his merry band of Intergalactic Pissed-off Krogan🥳
Humans With attitude (Let's face it, the humans are too stubborn to just die off anyway, and if Ash and James hooked up and lead them, not to mention Ken and Gabby, whoo boy! Look Out!)🥳👿
Asari with attitude, possibly including Matriarch Aethyta and her and Dr. Chakwas' blue babies (you know she's not gonna let Liara get too far away with this final battle, and she and Dr. Chakwas are just so similar in the attitude department...)❤️
The Normandy SR2
Also, If they hit Andromeda not long after the battle for Earth (either by Shepard using the Crucible or by a pissed off Catalyst firing it to take out the trash) and wound up having a clash with the Jardaan, possibly relating to unauthorized genetic tampering, they could be the enemy who is fighting the Jardaan, and they could have created, or triggered if someone else had created, the Scourge