Warning: Spoilers for Superman & Lois season 2, episode 15
Superman & Lois' shocking Arrowverse reveal hurt the chances of a crossover with The Flash happening in the future but doesn’t take it off the table completely. A speech from Sam Lane in the Superman & Lois season 2 finale confirmed that the show isn’t actually set on Earth-Prime. That means, of course, that the version of Superman depicted in the Arrowverse spinoff doesn’t know any of his fellow Arrowverse heroes, including Barry Allen.
Crisis on Infinite Earths’ game-changing ending laid the groundwork for some truly exciting Arrowverse team-ups, one of which being Superman and the Flash. However, an alliance between the two DC Comics icons in the post-Crisis Arrowverse has yet to become a reality. The Superman & Lois season 2 finale dimmed hopes of it ever coming to pass when Lane made a remark about Superman being the planet’s only superhero. That proves that Superman & Lois has its own Earth and simultaneously provides a much-needed explanation for why Supergirl and Flash are never called upon when Clark is indisposed or in need of help.
One of the many implications this reveal has for Superman & Lois’ future involves potential crossovers. Obviously, it’s now impossible for Barry to simply speed over to Smallville and help Clark take down a future villain. However, it’s important to note the Superman & Lois season 2 finale hasn’t ruled out the possibility of the opposite scenario coming to pass. Gustin may not be able to make a guest appearance on Superman & Lois as Barry Allen, but theoretically, Tyler Hoechlin’s Superman could still show up on The Flash. The ending to the Arrowverse’s Crisis on Infinite Earths event showed that Superman exists on Earth-Prime and is now a member of the Justice League.
Superman And The Flash Can Still Team Up In The Arrowverse
Since there is a Superman living somewhere on Earth-Prime, Grant Gustin's Barry Allen still has the option of joining forces with the Man of Steel if the situation ever calls for it. Such a team-up would naturally have to ignore all of the developments that have occurred in Superman & Lois, though, especially since everything that happened in the series wouldn’t be canon with The Flash’s continuity. In fact, The Flash’s Superman may still be in Metropolis with Lois Lane. Overlooking these things shouldn’t be a problem for The Flash, given that the focus would be on the dynamic between Clark and Barry and the prospect of finally seeing these characters interact with each other beyond the brief amount of screen time they've shared in previous crossover events.
Based on the number of popular stories they’ve headlined together in the comics, a Superman-Flash team-up has been one of the most talked-about ideas in terms of the different crossovers the Arrowverse could offer. It was considered a huge missed opportunity when The Flash season 8’s “Armageddon” neglected to use Superman, and because of the Superman & Lois season 2 finale, his absence from the event makes a bit more sense now. That being said, his inclusion could add a ton of excitement to Barry Allen’s show and certainly an avenue that the Arrowverse should consider for The Flash season 9.