4 Arrowverse heroes who definitely won't be back in Superman and Lois season 4
The Flash
Barry Allen is undoubtedly the Arrowverse's most beloved hero. The Flash was the first Arrowverse spinoff, coming after Grant Gustin debuted in an episode of Arrow, and it went on to become the most successful of them all, running for nine seasons. It made sense that it was the one that got the chance to close the shared universe out with its final season.
That said, fans have been hoping to see Gustin reprise his role on Superman and Lois for sometime now. Given the friendship between Superman and The Flash in the comics, it would have been awesome to see the Scarlet Speedster make his presence felt on the show at some point, especially as Gustin himself is a major Superman fan and he previously worked with Hoechlin's Man of Steel on the Arrowverse crossovers.
Unfortunately, of all the potential returnees on this list, this is the one that is probably least likely to happen. Gustin is currently starring in Water For Elephants on Broadway and Superman and Lois is over halfway through filming on its final season, so the likelihood of him making even a cameo appearance on the show is essentially impossible.
It would have been awesome to see the Arrowverse's greatest hero show up on its last remaining offshoot at least once, especially because the writing on Superman and Lois is of a far higher quality than The Flash's final few seasons, but the stars just didn't align. Maybe it would be a different story if the show had been given that fifth season it was supposed to get.