ThoughtStreams hasn't brought in a huge amount of revenue (right at the moment it's actually generating none because we've made the public site free in the hope people will pay for a private, team-based version).
However, it doesn't need to.
Eldarion is profitable and doesn't rely at all on ThoughtStreams. We have a very long-term outlook on ThoughtStreams. I still believe it fulfills a need nothing else does.
We will always make it easy to export your content, we're looking into ways of better integrating with other systems and even if, for some unforeseen reason, we stop active feature development, there's no reason for the content on the site to ever go away. I have a personal investment already of 1,000+ thoughts here :-)