If the current device is a HART 5 product, for example Device Revision 0x01, these are the available paths forward:
Update to Device Revision 0x02 and remain a HART 5 Protocol product.
Update to Device Revision 0x02 and update to a HART 6 Protocol product.
Update to Device Revision 0x02 and update to a HART 7 Protocol product.
The other options available for a HART 5 device would be:
Request a new Device Type Code and start with Device Revision 0x01 using the HART 6 Protocol.
Request a new Device Type Code and start with Device Revision 0x01 using the HART 7 Protocol.
If the HART Protocol version is updated, any future device revisions must implement the same or a newer HART Protocol Version.
Device Revision is a single byte unsigned integer returned as a data field in the Command 0 response ("Universal Command Specification" HCF_SPEC-127 revision 7.1 section 6.1). The use of Device Revision and the update rules are found in "Command Summary Specification" HCF_SPEC-099 revision 9.0 section 6.