Given that DC’s announcement seems to indicate that Lois Lane won’t debut until the crossover in December, Superman will likely pop up on his own in his early Supergirl appearance.
Superman hasn’t appeared in the flesh on any Arrow-verse show since the end of Supergirl Season 2; the Man of Steel’s return should be welcomed by man fans.
Now we may be able to count on him on multiple Arrow-verse shows this year instead of just Supergirl, with the exception of Legends of Tomorrow.
The news (courtesy of DC Comics’ official Twitter account) confirms earlier hints that Tyler Hoechlin could reprise his role as Superman in the 2018-2019 season, although all signs at that point only indicated that he could drop by Supergirl shortly after it returns in the fall.