No, there is not. People get hung up on this for false reasons. There is no reason to upgrade any existing rule. It will continue to work, continue to be editable, and be clonable, etc. It is a false concept that there is some advantage to upgrading old rules -- there is NO advantage. For many people, upgrading rules is an OCD thing, like I'm missing out on something if I don't upgrade. You're not missing out. If you want to take advantage of new features in 5.1 that weren't in 5.0, that's not something that implies needing to upgrade a 5.0 rule, that's something that suggests you should create a new 5.1 rule to utilize those new features.