The very first F30 mule was publicly spotted/photographed in Nov '09 IIRC. And it went on sale in the US in Feb '12. So based on that ~27 month turnaround, we could see the F82 in very late 2014. Maybe even early '15.
And I think the F30 chassis will see LCI for MY2016. So all you folks that get an F80/F82 in the first 1-2 model years, don't be getting all mad when it changes shortly after!