The CW Arrowverse has grown into one the biggest comic adaptation universes, with shows including The Flash, DC's Legends of Tomorrow, Arrow and Supergirl (and many more to come). What makes these shows stand out is that they are able to intersect on a seasonal basis thanks to the now-fabled series crossovers.
Beyond those events, one of the most fun parts of DCTV is the infinite possibility for character death, rebirth and personality switches thanks to the multiverse - alternate realities that can be vastly different to the one we know. These versions show up frequently on series like The Flash and now Arrow, although don't expect this to grow into a bigger part of the Arrowverse fabric and move over to Supergirl,.
According to a TVLine interview with Supergirl executive producer Andrew Kreisberg, we won't likely see any major events with the alternates anytime soon:
“The problem with that is if we do that once, we’re going to open the floodgates of insanity.”
Kreisberg goes on to say that if it was a really good story the possibility would still exist - so if they can craft a huge event that is worth all the headache of keeping the alternate versions straight, the future could hold something interesting. The multiple versions of major characters are starting to move around the various series already, like Captain Cold moving from The Flash to Legends and alternate Laurel Lance also shifting there from Arrow.
The multiverse has become a huge part of most of the DCTV series, with the exception of Supergirl, although it does seem like only a matter of time before the alternate universes break through in National City. There's definitely a lot of avenues to be explored with alternate versions of Supergirl - there's comic grounding for the likes of Power Girl, Matrix or Ariella Kent, as well as pre-Crisis vs post-Crisis versions and Bizarro depictions.
There's still plenty of room for standard crossover events, of course. Supergirl and The Flash will meet for their musical episodes in March, and there's hope for an all-out four-way crossover event next season. The primary concerns seem to be the shooting schedules of the shows and availability of the actors involved.
Supergirl airs Mondays at 8 p.m. on the CW. The Flash airs Tuesdays at 8, with Legends of Tomorrow following at 9. Arrow airs Wednesdays at 8 on the network.
Source: TV Line