https://tvline.com/2021/05/25/the-cw-fall-lineup-2021-riverdale-tuesdays/
The Big Moves
♦ The Flash‘s five-episode event will feature crossovers with TBD Arrowverse characters. “We’re talking about other superheroes from the CWverse that will come together in each [of the] individual episodes,” says CW CEO Mark Pedowitz. “That will not quite be a crossover but it will have a crossover-type feel at the introduction of all these characters.”
♦ Batwoman and DC’s Legends of Tomorrow are also on the move, with both shows fleeing Sunday for Wednesday. (The CW is turning Sunday nights over to game shows.) Nancy Drew, meanwhile, will shift from Wednesdays to (gulp) Fridays.
WEDNESDAY
8 pm DC’s Legends of Tomorrow (new night)
9 pm Batwoman (new night)
ETA
Deadline has a article with more details about the five episode Flash crossover and the launch of the next seasons of shows.
https://deadline.com/2021/05/the-flash-5-season-8-premiere-event-will-crossover-riverdale-season-6-the-cw-fall-2021-1234763878/