Steamworks Documentation
Tip - Renaming a live exe

Situation

You've got a released game with customers already playing it and you need to rename your exe.

Solution

The order of operations can matter here, as setting a build live doesn’t go through the publish process but changing the launch options does. If it’s only a few seconds between the two, it’s unlikely to impact many people as Steam will force an update when the user goes to launch and that should grab the latest launch options. Assuming that there’s a build update associated with the change, we recommend setting the build live and then immediately publishing the app admin settings with the launch option change.

If you’re particularly worried, you could duplicate the EXE (with both names) for the transition build and push that live well before you make the launch option change. This would ensure that clients have time to grab the new build (while still being able to launch) before the launch option change came through.