It seems to me that Leica has alloted a certain number of M8 to each dealer so each dealer know how exactly how many M8 he will receive on the first shipment. If you are one of the top five and the dealer is going to receive more than 5 M8, you should be among the first to receive it.
People that went to Leica in Solm saw boxes of M8 at the time 0f Photokina. They reported that Leica plans to ship all 2000 units worldwide at the same time. Allow a few weeks for softwear installation and delivery(both to Leica USA and then to dealers). My guess is at least November or later.