We can't say for sure, I don't recommend using Joomla 1.6.x until another 1-2 months to give developers time to play "catch-up". We're still making fixes and performing tests as necessary. You can follow our progress at our forge at the following URL.
forge.joomlapolis.com/projects/cb/issues?set_filter=1&tracker_id=1
This is a massive undertaking, it's not a simply quick fix and done overnight. We've to be EXTREMELY careful about changes to avoid breaking Joomla 1.5.x, Joomla 1.0.x, and/or Mambo.