Preview at WWDC likely in June, followed by September launch.
iPods in Unreleased Colors Spotted in iTunes 12.2
The new colors include a darker blue for the iPod touch, a new gold or beige color for the iPod nano, and a brighter pink color for the iPod shuffle.
Apple has not updated its iPod color lineup in several years, most recently shifting the previous "slate" color to "space gray" back in 2013. Apple has typically updated its iPod lineup during the month of September, although it is unclear whether these new colors are actually in the works and what their release timeframe might be.
Update: Several observers have pointed to the Calendar icon on the iPod touch screenshot showing a date of Tuesday the 14th, leading to speculation the new models could launch on Tuesday, July 14. Readers have also noticed the new image does not depict a wrist strap attachment post as seen in the lower left corner of the current models.