Since April's predictions, three things have happened concerning this category.
1. Mo'Nique's buzz continued to grow for Precious (formerly Push: Based on the Novel by Sapphire... why hasn't the IMDB changed this title? It's been weeks, nay, months)
2. The NINE trailer debuted and surprisingly it hung on Judi Dench's dry humor and Fergie's vocals rather than on Daniel Day-Lewis or his three paramours (Cruz / Kidman / Cotillard)
3. Cannes didn't do much for Imelda Staunton's buzz for Taking Woodstock. Though folks in the know expect reaction outside of Cannes to be more favorable since the film is light and funny. Cannes isn't so big on light and funny.
Dench could still be tripped up should she not win "best in show" reviews or if the film disappoints. But Mo'Nique is good to go. We already know that Precious doesn't disappoint. More and more people are fans. I suspect it will be a major player at the fall festivals (Toronto & New York) before its theatrical launch.
UPDATED PREDIX - Supporting Actress