Full Siri integration isn't necessary. What is important is to integrate with Reminders, which can be used as a 'pre-inbox' or as a separate tracking tool like your Calendar. If you think about it there is a need for such a tool, already in one day I'm using Reminders this way.
- Reminders This is the hopper. Ideally it would be the OF Inbox, but it can serve as a pre-inbox. A lot of stuff goes in there (quick one offs), if it's important or bigger it can make it to the more formal OF database.
- Calendar Hard landscape important events.
- OmniFocus More important longer term project tracking etc.
naupaka has an interesting approach which I'll investigate.
Again - I don't think Siri integration should be the focus right now, Reminders fits a tasking niche that OmniFocus needs to work with, just as it does for iCal.