I'm afraid that since the Ubercart dev team decided to make changes for the Drupal 6 version that it could take some time. A simple port to Drupal 6 would have been much faster. Though since the version they are working on for Drupal 6 is set at 2.0, it is still possible that they could quickly put out a 1.0 version with just the basic API changes needed to make it function properly with Drupal 6.