When would a GT3/GT3RS .2 generally be out?  1 year from September?  Or longer?

Difficult to say. If I had to guess, then 2016 will be a year without GT3 production (so no MY2017). 991.2 GT3 presentation at IAA in september 2017 and 991.2 GT3 RS (if they will build) presentation at Geneva in 2018... 

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Porsche 911 GT3 - Guards Red 997 MKII Clubsport