I thought the point was that there's a covenant on the land requiring it to be used as a sport's ground, rather than a planning thing?
Whichever, I think it's up to CF Booth to come up with a proposal for redevelopment. I don't see any point in knocking it down for the sake of it. I mean, the rugby club might, conceivably, be in a position to make a more commercial offer to use it one day.
That said, if there is a genuine case for redevelopment, I don't see there's any longer any point in standing against it just to be obstructive.