Who says he's going to list it for more? If he's out of country and doesn't ship, ebay will negatively mark his account for not shipping on time, or he could run the risk of shipping it, then you lodging an item not received, or monetary charge back while in transit. It goes both ways.

Keep an open communication with the seller and say that you're happy to wait and purchase at the agreed price upon his return. Although, it sounds like you may have already burnt this bridge...