I've just finished rewatching Silence in the Library, and Forest of the Dead, the two episodes of Doctor Who where River Song is introduced. So much potential is introduced in this story, that it's not entirely surprising that fans feel let down by how River's story has played out.
The Doctor has rebooted the universe once, and restored it a second time when all of history occurred at once. He faked his own death, but the future for River remains locked up in the library.
I preferred River as an enigma, where her cryptic spoilers hint at untold adventures, rather than reveal a more mundane existence.
It's perhaps telling that one of the major story points for River Song was dropped into a mini-episode: her last night with the Doctor before the Library. The moment where the Doctor gives her his sonic screwdriver, knowing that the next time she meets him will be her last. It's included as a bonus feature for a DVD or Blu-Ray boxed set, but as there are no real plot points, aside from our knowledge that this is her last night before the Library. It's a gimmicky short, and wastes a good opportunity with something a little deeper.
In a way, it's good that this was an Eleventh Doctor mini-epsiode. The Doctor taking River out on dates seems very much like Eleven. I really think we'll get a much different Doctor out of Twelve, and one of the things that should feel much different is his relationship with River Song.
I'm torn between wanting to see how the Twelfth Doctor and River Song negotiate their relationship, and wanting to see Twelve find himself alone, then finally rediscover River. Perhaps it's too much to ask of Moffat to set River Song aside for a series? It might actually build up a bit more emotion if he finally encounters River after some time apart.
The thing about River is that there's always room in her history for her timeline to cross with the Doctor, and get another episode together. But is that enough to justify doing so? Knowing Moffat, we will see River again sooner rather than later. If there are any other mysterious aspects of Doctor Who, Moffat will shine a cold, hard light on them, dispelling any of the magic.
I just hope that Moffat leaves River's future in the Library.