I'd prefer we never actually see the last of River, she's fun as an occasional guest.
As I have stated before, I believe that as long as Moffat is writing the show, there's always the possibility River will return. Even if he continues to contribute a script every season or so after he steps down as showrunner. The only limiting factor will be Alex Kingston's availability.
Which is really strange when you think about how the Doctor says he could always see her. That means that she's followed him around for (at that point) about 300 years, watching him have adventures with all sorts of people, including herself. She got to watch how the Doctor experienced their relationship. She got to see her own mother snog the Doctor on the night before Amy's wedding, for instance. All along, River might have been talking to him, and he ignored her and pretended he couldn't see her.
That's really strange. It's an interesting idea when you think about it, but as a practical matter, it's almost unbelievable.
One has to wonder, how did data ghost River not give away any hints hinting at Amy's importance when the Doctor first met her. Even if the Doctor was actively trying to ignore River, there had to be some difference in her behaviour when Amy was around to give it away. You can argue real River never had any tells to give it away, so ghost River shouldn't either, but real River had the advantage of occasional privacy from the Doctor, which ghost River didn't, increasing the chance of slipping up at some point.