It has been renewed for a 6th season....
http://www.tvsquad.com/category/curb-your-enthusiasm/
Vivica A. Fox will be joining the cast of Curb Your Enthusiasm for the show's sixth season, which kicks off next year. According to Hollywood Reporter, there's not much information, though information points to Fox playing the member of a black family who moves into the David's home after a natural disaster. So there you go, Vivica A. Fox will be playing a black woman, and frankly, I couldn't be happier. I was starting to grow tired of seeing her constantly playing an elderly Chinese man. The storyline is meant to spoof the events of Hurricane Katrina, as well as race relations. I imagine we can look forward to Larry saying something incredibly inappropriate. The article doesn't mention whether Fox's character will stay on the show or whether she'll only be part of this specific storyline.