Guess they posted it early.
TLDR: Dr.Mundo is nearly done, preview images of 2 best skins; Yordle got delayed, her design is now a traditional mage instead; Sentinel of Light will come first, and it's a midlane ADC; early concepts of Udyr; New teaser of the botlane ADC which looks like Zaun related.
Edit: For the teaser they used the term "the toughest race of Runeterra" along with the ADC, from the wording I don't know if it's an extra description of the ADC or it's for another champion which will be support.