Yep, they will moan, threaten to leave, get a few sales on eBay and pay the higher fees and then forget about it until the next increase when they will repeat it all again.
Where eBid may benefit is the few who find that their slim profit margins become non existent, and from sales where those on eBay increase prices in order to keep trading profitably. They might only be small nails in the eBay monster but it could be death by a thousand cuts.