I think Shushu has a good chance at winning this. She's beaten Vera before, and she can beat Aga if she holds her head together.
As for Petko, the two of them haven't played since 2007. But I think Petko would win that match.
Peng should be able to get to the SF. The other top seed in her quarter is Ivanovic who is pretty useless and might even play Morita again in her first match... If she gets to the SF, she better hope that Zvonareva beats Bine or else she's screwed. But the winner of the top half should probably win the whole thing.