At Day 0 of AVEVA World in San Francisco I found out that the AF SDK is finally being updated to a .Net Core version, meaning support for later versions of .NET (ie, .NET 6, .NET 7, and .NET 8). No timeline as yet for the release, but it will be "soon". A few hours after this conversation at the Moscone Centre I saw the email come through from the feedback site. See Upgrade .NET version support for | AVEVA PI System
Feedback Portal.
One of the key reasons usually given for not going beyond the current version was lack of support for WCF in later versions of .Net. Turns out this was not the major blocker, as the WCF functionality needed for communication between AF clients and the AF server will be replaced with gRPC.
This will be welcome news for many in the developer community, and those customer organisations running applications built on the AF SDK and thus limited to an older .Net Framework technology stack.