Their departure will be in Season 6’s 13th episode.
I’m much more broken up about Lowe’s departure than Jones’. Rashida Jones is a fine actress, but Ann Perkins has always been one of the more problematic characters on the show. Cast shakeups happen all the time (and have to this cast before), so there’s no reason the show can’t go on and be just as good or better (in a different way).
Aw so this means that they either end up together or hating each other so much that they both start completely new lives, I love TV romances