Back from holiday, so figured I'd add my $0.02.
Traffic is definitely down, and that's probably the case across the site. Modding both here and the F1 board, it's noticeable in both places. I hope there's no common factor there...
I think the main problem is that as a community we mostly originate from the old 606, well over half our members have a join date of January 2011, when the switchover happened. Since then, people get fed up, angered or whatever and leave, and we don't have the influx of new frequent posters to pick up the slack. I guess forums are becoming somewhat of an internet backwater as everything seems to happen on twitter, facebook, etc these days. As the number of posters drops, the site becomes more of an echo chamber and we're all somewhat familiar with each others positions on things, so when there isn't fresh news then there can certainly be a drop in activity.
As to how we can reverse that, I guess the first thing is to appeal to any lurkers to sign up and get stuck in. Despite what I've just said, we're a friendly bunch and new input to debates is always welcomed! The other options are to "advertise" ourselves in some way, or to increase the quality of content and hope that leads to new people joining.
On the first option, we have a twitter account bot which just churns out links to new threads with appropriate hashtags added. Perhaps having that account be more active in twitter debates and see if it can persuade people to join might work. Personally I don't have the time to really do such a thing, hence it being a bot. If anybody wants to try this route you're more than welcome, hopefully I can find the account details! I guess other options are persuading friends from the real world to sign up, or trying to get the site name out there when some of us comment online elsewhere.
As to quality of content, I guess the summer is always a low ebb for that. If you don't like transfer rumours then there's meagre scraps available. If people want to try running forum games, please do, or start any discussions that come to mind.
Unfortunately, as with many things, identifying the problem is much easier than solving it!