Well the council races are a given, so i'll skip them.
So who else might be coming?
Well I highly doubt the Turians would abandon their client races. So I am sure the Volus will still be around, they just might not have any big roles. Likewise I could see Krogan, depending on the type of Krogan coming along, would bring Varren and Vorcha with them. Maaaaaaybe not Varren if they have strick resource issues but who knows.
So the species most likely to be left out are Hanar, Drell, Quarians and Geth.
Hanar and Drell both have pretty strict living conditions that might make ark travel difficult. I honestly can't say if we will see them in ME:A. As a non human, non biped species they will take resources to make models for and animate. Their main purpose in ME was their connection to the protheans, who might not be relevant at all anymore and if we don't get Hanar we won't get Drell. Drell just don't have the numbers otherwise.
Quarians and Geth will be tough. I know they said they won't be taking ME3's ending into account, but until near the end of the game both species were at war with each other, and the resolution of their story arc potentially leaves one of these species destroyed. If they give us both, unless they decide to completely ignore all of that, I don't see how we will have either of them.
If we do get them, Quarians are much more likely and make more sense.