Parks and Recreation is casting for several new characters for the upcoming Parks and Recreation Episode 9 called Ron and Diane which we will see late November / December.
There isn't a lot of information about it other than the name of the episode and character info but it's a good bet to assume Lucy will be back as Diane.
Lucy will next be seen in the 5th episode called "Halloween Surprise" and that will air on NBC 25 October 2012.
For more about Lucy's role as Diane on Parks and Recreation Season 5 visit the AUSXIP Lucy Lawless Parks and Recreation subsite