I don't have a real answer, but I got the impression that it was more of a battery module allocation issue with Zero. I think all of their bikes use the same battery module and I believe that all of the production is going into the batteries to power the production motorcycles. I think I got mine because I griped about it to my dealer and one was grabbed off the production line and shipped to my dealer to be installed in my bike. (Or I could be a Zero beta test rider for the power tank accessory.
) Once the dealer demand for the 2014 bikes has been satisfied, I suspect that the "power tank" kits will be distributed quickly. But, I always say: "The squeaky wheel gets the grease".
I might also add that my dealer drove down to the factory and picked up the power tank in person so that it could be installed in my bike ASAP. That was great customer service, especially as it was raining the day and the factory is located about 90 miles away from the shop.
Speaking of not getting accessories: I am still waiting for my Zero windshield, rear luggage rack and top box (which I have already paid for) to arrive. (Squeak, squeak) I guess things are pretty busy down in Scotts Valley this year.