Sharapova has a better record against Williams than Azarenka (VA has only beaten Williams once), and she's playing really good tennis at the moment. That said, Sloane Stephens is very capable of causing an upset against Williams. In the US they see her as "the next big thing in American tennis". They have never met in a grand slam before either.
For the men, honestly the way Federer is playing at the moment, I think he's unstoppable.
wtf you are talking about stuff that happened in 2004, its 2013 now so its been almost 10 years since sharapova won against serena and 5 years since she has even won a set
in the meanwhile since sharapova has failed to win a set against serena, vika has beaten her, she served for the championship against her at the very last grand slam, she won this tournament last year and in another australian open she retired while a set up against serena
clearly the only one left who can stop williams is azarenka, maria will be praying for a vika win assuming she can win her semi but basically serena will probably destroy them both
its not 2004, but its also not 2015 either so stephens has no chance to win a set unless serena doesnt believe in black on black crime and shows mercy for a while