To be brutal, most of the material inherited by this forum is legacy and has little relevance on how to play the game now. It has an historical (and, for some of the older participants, a nostalgic or emotional) significance, but not a commercial value.
More recent material? Well, the mushrooming of independent forums shows how easy it is to get something up and running. So, again, no commercial value.
I don't know what value a membership list has nowadays (possibly in attracting advertising?), but would doubt that it has much.
If MA owns the forum, then presumably it loans it out to whoever owns the planet. If it doesn't own the forum, there shouldn't be any commercial incentive for the current owner to hang on. Whatever, the forum will follow whoever manages the planet.
In a multi-forum environment, there are only two reasons for having an 'official' site: (1) for archiving (which is why the early howls about the sale from EF to PCF seemed strange - an official forum should have more survival power than an unofficial one); and (2) for contact with the game's paid managers and developers.
So the logical conclusion of this argument is: this forum is likely to move onto whoever takes control of Calypso after MA's stewardship ends. So it should remain an important forum, the more so if it acts an an interface between managers/developers and players.