I thought the first option given for the XII is white flint grey (attached picture), and the confirmed to be released is Retro White/Black-Taxi, or I might bewrong?
^^^^ Call up Nike Park on a daily basis a week before release date until they tell you the stocks have arrived. When they say the stocks are there, dropwhatever it is you are doing and just go straight to the store and get your set
The XI/XII package will be the most in demand package, second only to the DMPs so don't take any chances. Hope this helps