I believe Windows 11 will be 64bit only, so I guess that means no more NTVDM and no more win16 support. In that case, there won't be any windows 3.1 16-bit code left over. On the other hand, win32 was designed to be mostly source-code-compatible with win16, and I'm sure you'll find elements that have been given a minimal win32 porting effort, while a "git blame" equivalent would probably trace back to windows 3.1 still.
On the other hand, 32bit Windows 10 is still going strong and there are probably plenty of windows 3.1 (and windows 3.0) applications that would still run there.