Certainly, that would be the ideal setup for Siri on Mac. But I don’t think Mac Siri even has support yet for third-party apps. Combine that with this week’s revelations about backend disorganization regarding Siri at Apple, and that type of functionality looks a long way off. Personally, as someone who prefers the speed of a Spotlight-style interface since it doesn’t have the lag that comes with voice recognition, I would stick with Spotlight Search Prompt from @DanThomas even if I had a Siri-equipped Mac (and I figure I eventually will).