Well, contrary to popular belief, Nyck de Vries will indeed be staying in F2 BUT will return to his GP3 squad ART. Nobuharu Matsushita (who was teammates with Vndoorne and Sirotkin in ART between 2015 & 2016) will be returning to the series after spending 1 year in Super Formula with the regining teams champions, Carlin. Nirei Fukuzumi and race winner Tadasuke Makino will be heading to japan for Super Formula.
the de vries decision I find very interesting as it was widely expected he would be joining audi in DTM and until recently, ART was in the DTM.
EDIT - Calderon is testing for Charouz