Arrowverse: Age of Heroes

This is what I predict for Arrow season 6, The Flash season 4, DC's Legends of Tomorrow season 3 and Supergirl season 3.

(when the currents seasons end, I will make some changes)

Supergirl

 * There will be an event that will merged her earth with Earth-1


 * Special appearances: Batman, Mr. Freeze, Aquaman, Ocean Master, Blue Beetle, The Reach, Power Girl

The Flash

 * Special appearances: Batman, Poison Ivy, Shazam, Black Adam, Raven

Arrow

 * Special appearances: Batman, Joker, Green Lantern, Sinestro, Black Lightning

DC's Legends of Tomorrow

 * Special appearances: Batman, Terry McGinnis, Derek Powers, Wonder Woman, Ares, Captain Atom, Booster Gold