Re: Silence in the Library/Forrest of the Dead in retrospect
This is the Whovere y'know - there must be an infinite number of ways to provide River with a physical form for her consciousness to be downloaded into. (Why couldn't she just operate a remote body made of the Flesh?)
Technically, River is also now immortal. Her actress notwithstanding, within the fiction the Doctor should be free to meet up with River again and move forward synchronized in time. If she is given a new body, it could easily be as immortal or replaceable as the Doctor's.
Given that River is tied to the 11th Doctor's story, I'm assuming they'll want to wrap up her story at or before the end of the 11th's tenure. Given that she's the Doctor's wife, I'm thinking they will somehow give her a grand send off. Given that there's precedent for linking the TARDIS and the Doctor's wife, I'm going to make a wild guess here, and say she'll be somehow downloaded from the Library and uploaded into/fused with the TARDIS. Or maybe not.
Now all I want is to warn earth: watch Farscape... and share the wonders I've seen.
It's Tolkien, not Tolkein.