I am not an expert at authentication but I am on things relating to eBay and I have to tell you that if you are the winning bidder of this auction you are required to pay for it. By placing your bid you entered into a contract with seller and it is your obligation to honor that contract. If you do not pay the seller can open a dispute which will result in you receiving a strike against your eBay account. You will need to pay for the item and wait until you receive it. If it turns out to be a counterfeit as authenticated by one of the experts here, you can then open an "item not as received" dispute and subsequent claim. That way you would be refunded your money and no strikes would be issued against you as a non-paying bidder.
Good luck!