I don't know a lot about the current ALMS regulations and what would need to be changed to get the Z4 GT3 into the series, but there are some indications that the ALMS will open up the GT class in some way next year and there are rumors that the GMG Audi R8 might be taking part in this year's Petit Le Mans. ALMS can't ignore the growing GT3 fields across the world and expect to stay relevant. With the reduced numbers of LMP1 cars on the grid and the possibility of having a GT field of Ferrari, Porsche, Corvette, Viper, Lotus, BMW, Mercedes-Benz, Audi, and McLaren they would be fools to not seriously consider it. With the correct balance of performance between the cars it could be epic!
But either way it will be a shame to not see the M3 GTs next year and I'm still upset with BMW Motorsport for not wanting to support RLL going to Le Mans.