I don’t have one to one visibility in metrics. Looking at the number of users who have earned Karma on answers.ros.org there’s about 50% more on ROS Answers than Robotics.SE.
It’s still early but we have seen significantly increased engagement on Robotics Stack Exchange since the migration with double to triple some of the very basic site statistics.
I’m sorry that you didn’t get a chance to do the association. We’ve been messaging with the specific link to sign up since May and June about getting people to register.
The migration has been completed. There’s a question on Robotics Meta Stack Exchange which has the best known solution to try to associate your data now.