setproctitle is quite stable, my company uses it in production environment very heavily with python 2.x. Probably its users base is not huge, but that's because it's a relatively specialized tool.

Python3 porting is not straightforward because python2 exports the original argv pointer using Py_GetArgcArgv() whereas python3 only exports a decoded version in a wchar_t* array. This may not be a showstopper: probably the original argv can still be found scanning backwards from environ: I want to test it but I haven't had requests for it yet, so it wasn't a top priority.

So, while I'd be pleased to have it included in the stdlib, I'm not really convinced it would be useful to such a large audience. Anyway I'm available for any improvement it would make the tool more useful and to anybody eager to push for its inclusion.