I can't see dual disc taking off for stocks, easpecially for comps. The spoke flex just doesn't make the bike as accurate on the rear wheel, plus most comp riders couldn't cope with the extra weight.
For mods dual disc is amazing, I would definitely be using it if I rode one.
Street 24" is also pretty good, I have 180mm saints and I'm pretty happy with them, sometimes there is a little slip, 200mm rotors could help that, but I'd rather have smaller rotors that are harder to bend. Not too sure if TGS or even comp riders would be overly keen on them as they still don't feel quite as direct as a rim brake.