We want to keep them completely separate from the start. The Filecoin mining community is already very distinct from IPFS users, but more importantly the world around Filecoin (cryptocurrencies, ICOs, etc) is a much noisier space with a lot of vitriol. While there are inoccuous Filecoin topics like buying hard drives to build your storage mine, Filecoin miners will also need the freedom to discuss topics like sale economics and token valuation. Topics like those attract a special kind of troll and they can get ugly fast. We want to shelter the IPFS community from that distraction -- those discussions are essential to Filecoin but they are not essential to IPFS. Obviously many people will participate in both communities but they wil be distinct communities with distinct priorities and distinct norms.
The main limiting factor on spinning up an official Filecoin forum is the need for dedicated moderators - the Filecoin forums will require much more attention and moderation than the IPFS forums. The Filecoin team are still busy running the token sale. When that's finished they will be able to regroup, assign moderators, and spin something up.