Certainly interesting.....
Perhaps the Doctor returns to the library......
I mean, we saw all of River's timeline, from when she met him, to when she died. I do not see how she could come back, as she is dead and trapped inside of the Library's computers(I am really not sure if this really counts as a spoiler, as we knew this from the start with River).
The only time we saw River was with the TARDIS. That was because of the TARDIS's deterioration. However, that is a false reality now within the Doctor's timeline as well... So that never technically happened... Sort of....