She's only banned if she misbehaves again. Follow quote from here
Babcock confirmed that Serena acted outrageously and violated the 'major offense' rule for aggravated behavior. For that, she was fined 82,500 dollars, and was also given a 3-year suspended ban from Grand Slam events. The 3-year suspended ban means that Serena will have to be on her best behavior till 2011 to avoid incurring the ban. Additionally, her fine will be double to $175,000 if she breaches the 'major offense' rule in any Grand Slam event till 2011.
I'm glad she got a reasonably sized fine now (I know it is still nothing for how much she earns).