we are using Microsoft Sync Framework 2.1 in various customer projects for file and database sync. Extended Support will end in 2021.
So my questions are:
What is Microsofts strategy for the sync framework? Is it going to be open source, so we can change if needed ourselves? Is there a successor product that we should / can migrate to?
Is MSSF supported on Windows 10 and Server 2016?
Not sure if my answer really helps, but lets see: Microsoft announced the official release of the "Azure SQL Data Sync" on June 18 2018. It is not truly a successor of the original framework, but it is basically all you get. Other "non cloud" frameworks have also started to fade away, since Microsoft treats server/desktop/on-premise only as an extension to the cloud. As the name indicates, it is targeting Azure and it is not for file sync, either.
I have seen your question also in the "old" Microsoft social network (social.msdn.microsoft.com/Forums/en-US/home). In there they point to this framework in questions related to the original "Sync Framework" since something like 2012 (this was the oldest question I could associate with both frameworks).