There was an issue with the belt drive themselves. Last I heard, the bikes were completed but there was an issue with the belt itself laterally derailling from the cogs. Rather than ship and solve warranty issues and spoil the system, it is being delayed. Given that Trek's model years are August-July, I would expect to see it rebranded as a 2010 model and not to be released until August as such.

This is not from an official source, but I'll say "someone familiar with the subject"