MAYBE a trading sub forum will be in order in the future, but first we need to see how trading will develop in the 07 servers and the trading activity on this site. Trading is a priority in my opinion and also a concern on how to involve mediators to assist in such trades. We will also adapt to our traders requirements for 07 servers trading but for now we need to take out any risks which may occur during such trades, trades that as of yet we can't predict how they will be managed, since the servers are not online. The current trading section will do just fine for now.
About a new sub forum for general discussion about the old servers, I just can't see it in the future. The current forum works just fine, peoples will still be debating old and new server activities, game play tactics, hints, guides and anything related to Runescape, without any flooding issues. It is just an increased activity, since many peoples came back to try the old server, an activity which can have a place in a single forum.