All clusters will need to be upgraded at a point. If you have metro availability enabled in your environment,  you will need to follow the best practices guide lines for it:

https://portal.nutanix.com/#/page/docs/details?targetId=Web-Console-Guide-Prism-v510:wc-metro-availability-upgrade-considerations-r.html

Specifically Nutanix supports the following replications:

• Between N to N-2 major versions and vice versa for STS to STS versions or LTS to STS versions.
• Between N to N-1 major versions and vice versa for LTS to LTS versions.