I run/have ran a forum of similar size, posts and members for many years now, also music related.
The thing to do is keep them moderated, keep an eye on things, listen to and respond to any big noises made by the members, new and old. There's always a status quo to keep with these things and it can be a tricky balancing act at times as I full well know.
Would be a shame to see it go for many reasons. It's a valuable and concise source for music and like minded conversation, whatever the subject. Forums are few and far between, but those that perceiver are of great value compared to the smash and grab nature of social media these days. The original social networks if you will.