In short, I'd await his response and I wouldn't send payment until he responded. If he doesn't respond then I wouldn't send the payment. If he doesn't have the diligence to politely respond when a question is posed, then I would be concerned with other aspects of the transaction.
The worst that can happen to you as the buyer is receipt of a non-paying bidder strike which, from what I can gather, doesn't impact your eBay status in isolation. He can't leave you negative feedback.
With any luck, you've hit the nail on the head and your bid was automatically accepted. He's lay on a beach taking a few days holiday with no internet access and will be profusely apologetic upon his return and confirm RMSD is no prroblem for the amount you have committed to pay. The previous 'poor comms' feedback doesn't necessarily reconcile with this outlook but you never know...
Good luck.