They haven't said that at all. They've been talking about it for quite some time, but no decision has been made yet.
If people were here just because of the sig campaigns, then that would probably be a good thing for the forum...
Yes but there are other sites which offer this now Bitcoin related sites and they are having some good traffic it seems I mostly read before sigining up for signature advetising.
No advertiser is going to pay much for people to post on a forum that gets hardly any hits. The reason they pay so much for this site is because of the massive user base.