We're sustaining Threadable by charging business users for business-specific features. Those features will actually be rolling out soon, and have to do with internal access control and integration with certain external services. We don't talk about that stuff on the site yet because it's still in beta, but expect to see it soon.
I definitely see Facebook groups growing in popularity, but we're a long way from getting rid of email. I think the reason Facebook Groups has been able to gain so much ground is because email-based products haven't really changed in a long time, and Facebook Groups provides a much better user experience. However, email is still the only place you can be sure to find everyone, and that's unlikely to change anytime soon, especially in business. Group communication products have a bunch of tiny network effects, one per group, and they succeed or fail on how well they can reach every team member.