Mailing lists will suffice for development. I think that not having any officially sanctioned forums will work just fine.
So then it should link the mailing list from the main page, not the forum. It will get swarmed. Mailing lists scale even worse than forums.
Personally I find mailing lists pretty inconvenient, though, I hate getting everything in my mailbox, and it feels like a step backward instead of forward. It is also not a good way to give technical support to merchants/users which are not unix dinosaurs like us.