I have a feeling that it may turn out like the Suarez situation. We'll keep him for another year and (hopefully) he'll play well to keep Barca interested and then go next summer. Hopefully this will also give us the proper time needed to find an actual replacement.
To be honest though, as much as I love Coutinho I wouldn't be devastated if he went. I feel like Firmino has the potential to be just as big of a star in the future.