You may think you have to wait for Siri to appear in macOS Sierra before you can talk to your Mac, but your Mac already has a way to listen to everything you say and to turn what it hears into text.
Once again, I am in a place where I can’t work directly with my servers to test the NetInstall steps and images, so… we’ll take a brief detour here to take a quick look at your Mac’s built-in dictation features.