One thing Bioware have made clear is that the story of Andromeda WILL continue to be told.

Disagree. IMO the Quarian tease in the game was just there to tell you that Quarians will be in the next Mass Effect game (and maybe characters in Multiplayer), while the "how did they get there and in what kind of problem did they run?" was always planned for the book. But we will see. 

Though unless they tell a Ryder Jr. story in a book, there is still nothing replacing DLC.