I think it's inevitable that eBay/PayPal will accept bitcoin. There has been talk of it for quite sometime and just yesterday Wall Street Journal posted about Braintree (PayPal subsiduary) accepting PayPal. You can read that article here - http://online.wsj.com/articles/ebay-payment-unit-in-talks-to-accept-bitcoin-1408052917
I just don't see them passing the savings onto the consumers to be honest. If they did it would eat at PayPals core business.
That's what I guess too, there could be some minor changes in fees if they integrate Bitcoin into their system their but obviously not as big as their savings will be at first. Braintree already did so to a certain extent anyway and there was no advantage for the consumer. One can argue that the protection they offer is worth the cost, but it will be interesting to see what happens when people realize that with btc you can have such service in a more convenient way. I think anyway they will have to lower fees to stay in the game and they will have to redesign their platform to accomodate such changes.