As we know the current top 5 after Australian Open looks like this:
1. Victoria Azarenka 10325
2. Serena Williams 9970
3. Maria Sharapova 9545
4. Agniezska Radwanska 7750
5. Na Li 6255
Ranking points that the current top4 players defend from Doha to Roland Garros in 2013:
Doha February 2012
: Victoria Azarenka (900), F Samantha Stosur (620), SF Agnieszka Radwanska (395).
Dubai February 2012
: Agnieszka Radwanska (470), F Julia Görges (320), semifinalists (200).
Indian Wells March 2012
: Victoria Azarenka (1000), F Maria Sharapova (700), semifinalists (450), QF Agnieszka Radwanska (250).
Miami March 2012
: Agnieszka Radwanska (1000), F Maria Sharapova (700), QF Victoria Azarenka (250).
Charleston April 2012
: Serena Williams (470).
: Timea Babos (280); Vika should play here after Miami tournament in April 2013; this tournament was played last year in February.
Stuttgart April 2012
: Maria Sharapova (470), F Victoria Azarenka (320), SF Agnieszka Radwanska (200).
Madrid May 2012
: Serena Williams (1000), F Victoria Azarenka (700), SF Agnieszka Radwanska (450), QF Maria Sharapova (250)
Rome May 2012
: Maria Sharapova (900), F Na Li (620), SF Serena Williams (395), R16 Victoria Azarenka (125), R32 Agnieszka Radwanska (70).
Brussels May 2012
: Agnieszka Radwanska (470).
French Open May-June 2012
: Maria Sharapova (2000), F Sara Errani (1400), semifinalists (900), R16 Victoria Azarenka (280), R16 Na Li (280), R32 Agnieszka Radwanska (160), R128 Serena Williams (5)
As we can see Vika, Aga and Maria have to defend a large amount of ranking points in this time period, and on the other hand Serena and Na Li will have great opportunities to gain more points comparing to last year. According to Serena Williams´s official site http://serenawilliams.com/schedule/
she is planning to play in Doha, Dubai, Miami, Stuttgart, Madrid, Rome and Roland Garros.
Vika´s official site doesn’t tell yet about her actual tour schedule: http://www.vikaazarenkatennis.com/tour-information/