There will probably be exceptions, but I expect them to be a pretty small percentage once the haggling over the details is done -- things are moving in the direction of paying most of the revenues to the authors, as it should be, and I suspect most authors would rather have their works be more available, and make some money from them, rather than have them simply languish out of print.
There's a bunch of work to be done yet, especially to work out the details of the registry that's going to manage all this. But assuming things continue as they're going, and the snags don't prove insuperable, it's looking like a win-win situation: works remain available more or less permanently, and their authors get the lion's share of the revenue generated from them.
Now the question becomes, how do I direct Google to really obscure works that would be useful to get online? We got this question the other week, from someone who desperately wants to get his hands on the long-out-of-print Elf Hill Times Songbook. I don't know if this even exists in any libraries, so it raises the interesting point that, eventually, there needs to be some way to feed the really small-press stuff into the process. (Although I do note that a copy has appeared in LibraryThing, so I should probably see if I can put the requester in touch with the person who has one...)