You should be able to review Release Notes for each release on the PDN. For Smart Investigate, there are release notes for 6.2, 6.3 and 7.1, which summarize the changes for each version.
Pega's application called E&I Rulebook handles inbound and outbound processing of the XML messages specified by SWIFT's E&I (Exceptions and Investigations) initiative, often referred to as ISO20022 standards. This application, which sits on top of Smart Investigate, complies with the workflow rules specified by SWIFT. It would be helpful to understand if you are planning to move to that communications method, as most of the banks have so far decided against adopting this other standard.
If I'm reading this correctly, then either 6.1 or 7.1+ can use the E&I Rulebook for ISO20022 standards?
Australia is adopting ISO20022 for the development of its New Payments Platform (NPP), so we are very much interested in the SI capabilities for this - some more details below from the world wide web if you're interested in what's going on here (page 36 - 37).