Yes, her story is technically done but the beauty of River Song's storyline is that the audiences can meet her at any point in her regeneration/life. The Twelfth Doctor already referred to his 'wife' in Series 8's The Caretaker but they haven't met on screen yet. Way back in Series 4's Silence In The Library, River alluded to meeting multiple Doctors - the Tenth and the Eleventh only make two. How she would react to an older, grumpier Doctor would certainly make for interesting viewing indeed. Better still, if Paul McGann does return then River could to at the same time, meeting two different Doctors in one TARDIS. She would certainly have fun with that, just as much as she would meeting Captain Jack Harkness. Aside from the main companions, it has been River and Jack that have made their mark the most on Doctor Who so a celebration of 10 years of Nu Who would be the perfect opportunity to revisit both these iconic characters and see how they react to a new Doctor who is very different to those they've met in the past. Working together on Arrow, Alex Kingston and John Barrowman have already suggested a River and Jack spin off. Unless the BBC decides to celebrate the 10th anniversary with a new spin off, then appearances in the show - or together in minisodes - might be the next best thing.