Actually, they didn't. They just didn't renew her contract for now. She's still a major player and is responsible for bringing their sales up drastically. According to a spokewoman, she will be back in the near future. They hired Beyoncé to do the next stream of commmercials, which I think is great. Her career needs a little boost. Besides, Britney's had her Pepsi run for the time being.
Sidebar: Brit's been nominated for not one, but TWO Grammys!