I do not see a reason why WinSCP should stop working after you upgrade the system, as long as the upgrade preserves all registry keys (what I believe it should).

WinSCP is security software. So you should always use the latest version. There should be no issues when upgrading WinSCP.

I have a client Running WinSCP 5.19.6 on a Windows 2012 Server and we will be upgrading the server to Windows Server 2019. Disregarding issues with any other application hosted on this server, if we perform an upgrade in place to 2019, should we expect WinSCP to remain intact or should we plan to re-install WinSCP? Also, if 5.19.6 continues to function properly after the upgrade, is there a compelling reason to upgrade to the latest version, other than the obvious reason that it has the latest features. Keep in mind, I'm thinking of maintaining the client's current capability with the minimum changes, so the fewer changes required, the better.