Looks like Roy Harper could be appearing again some time in season 6. A fan on twitter said to actor Colton Haynes that they missed him, he replied back with "Roy will be back very soon".
Marc Guggenheim shared this image of the Arrowverse Crossover 2017.
Ep 6 will be titled “Promises Kept.”
Marc Guggenheim has teased this image from Arrowverse crossover on twitter could this be the DC character Sandman.
Stephen Amell has teased that he'll be getting a new Green Arrow suit along with a new a trick arrow which will appear in the 4 way crossover and expect to see a more smiling Oliver.
Ep 7 will be titled "Thanksgiving".
Stephen Amell has hinted at that there will be a new voiceover intro for season 6.
Preview pics from the Season 6 Ep 1 “Fallout”: