Rob Lowe and Rashida Jones will be exiting the show in the upcoming Season 6 during episode 13, in February according to BuzzFeed. This means that the on-screen couple's on-again-off-again relationship on the show will have to come to either an end or the two will stay together.
The show's Executive Producer Mike Schur released a statement, pictured below.
Access Hollywood reports that Parks and Recreation’s hour-long season premiere airs on September 26.
— Tom McAuliffe (@TomMcAuliffe) August 1, 2013
Best of luck to Lowe and Jones! The show will miss them. Though I'm sure we'll see them in other projects very soon.