According to Executive Producer Andrew Kreisberg, a version of Bizarro is coming to CBS's Supergirl when the show picks back up in 2016.
Speaking on Kevin Smith's Fatman on Batman podcast, Kreisberg revealed that the villain, a twisted reflection of Superman - or, more likely in this case, Supergirl - would be coming to the show. "We've got Toyman. We've got Bizarro," Kreisberg said at around the 52:50 mark. It's been known for some time that Toyman would appear on the show, but this is the first reveal that Bizarro would appear.
You can hear the interview right here:
Kreisberg did not reveal which version of Bizarro would appear on Supergirl. Although Bizarro Superman, commonly shortened to 'Bizarro,' is the first one that comes to mind, there's also a "Bizarro-Girl," who hailed from a Bizarro-World like planet called Htrae, and who appeared in comic books just before the "New 52" relaunch.
Supergirl returns from its mid-season break on January 4, 2016.