Don't flip the IPv6 allow setting just because people are upgrading. Just upgrading versions shouldn't change this behavior. As much as most of us would like people to start deploying IPv6, the vast majority aren't going to be immediately post-upgrade, and changing this can change the firewall policy behavior by allowing v6 that previously wasn't allowed. Upgrades should never change the firewall behavior like that. At the time it was done, everyone using the 2.1 code base was using it for IPv6, so of course it tripped up quite a few people.