Yes I'm sure in book world they are sent to the colonies.
I also have in my mind somewhere that if Handmaids had 3 babies for a commander and wife then they had the promise of not needing to be a hamdmaid anymore. That they would go off a live a nice life of retirement for handmaids. Of course (if I haven't made it up in my head somewhere) I very much doubt it would have happened.
It would have been off to another family, jezebels or the colonies.
I think what we saw in the first part of the first series is how Gilead felt it was or wanted to be. And as the story has progressed we see the dark underbelly of it where it is chaotic and nothing like the projected ideology of how they present themselves.
I quite like that we are seeing the areas where there is fighting and how life is like there. It was always alluded to earlier as something far off and a long way from the 'order' that was presented in the time of Offred.