My final four are

Ivanovic
V. Williams

Wozniaki
Kuznetseva

Alternates would be
Sharapova if the shoulder holds up.
Safina

Outside shots in the top half
Azarenka
I would have said Lisicki but she's already gone.

Bottom Half Alternates
Jankovic
S. Williams

Outside shots in the bottom half.
Dementieva
Bartoli
Radwanska
Hantuchova

The bottom half is clearly the tougher half.
The Round of 16 in the bottom half could be a who's who of women's tennis.
The top half could have some nice names but with Lisicki gone and Sharapova just
making a comeback it won't be nearly as impressive.

Women's Tennis is in good hands right now I think.