If that policy does go into a effect, I really hope it won't cause some sellers to leave... I love ebay, I've gotten rid of some stuff I had, and I've bought a lot of great items.
I visit it every day just to see what's up for sale, what kind of good deals there are, you know... the basic crap. I try to be as honest as possible, I ship as soon as money is sent, and I pay as soon as I win.
I really hope that sellers will ALWAYS be able to leave any feedback they want. I mean, if you can't be honest in how a sell or buy went, what's the point having the system at all? I get that people can lie, but I think buyers do it a LOT more than sellers.