That is a great question. Currently struggling with motivation to create a new version. The last full version was for Joomla! 1.0 with a patch/band-aid for Joomla! 1.5.
I have started a version for Joomla! 1.7 and CB 1.7... very early on was mainly working on concepts as I am going to re-gut the plugin.
Current thoughts are to change CB Connector (CBC) to a 'framework' type of plugin that does some internal work and exposes it's own event triggers. Then have the forum, or other software be a CB plugin that reacts to CBC's events. My thoughts are this should allow a one-to-many relationship allowing CBC to log the user into multiple forums or other software.
But as mentioned above, with all of life's other events it is difficult to find the time and motivation to revamp CBC to the current generation of Joomla! and Community Builder (especially with Joomla! now going to a +- 6 month version cycle)... tough to keep it up to date.