Awesome. I was about to say that, because that is exactly one of the great benefits of the VC. You can also set the auto sw update and the next time you connect a new member it will be automatically upgrade by the master. Check out this article
http://www.juniper.net/techpubs/en_US/junos13.2/topics/example/virtual-chassis-ex4200-software-automatic-update.html
http://www.juniper.net/techpubs/en_US/junos13.2/topics/example/virtual-chassis-ex4200-software-automatic-update.html