Despite CBS President/CEO Les Moonves announcing in March that all of the network's freshman shows would be returning in 2016, The Wrap reports that Supergirl may be dropped over budget issues. According to the online Hollywood trade, CBS is balking at the Warner Bros. Television-produced series' $3 milion-per-episode pricetag - considered one of the highest per-episode costs for a new show.
According to The Wrap, Moonves and Warner Bros. TV chief Peter Roth are set for a "last-minute staredown" over Supergirl's budget and its future at CBS. The network is scheduled to formally announce it's Fall 2016 line-up in two weeks at the annual upfront presentations.
It CBS and Warner Bros. TV can't come to an agreement, it's possible that Supergirl could be shifted to the CW - which Warner Bros. co-owns with CBS - however the budget issues would conceivably be even more of a problem there.
The final episode of Supergirl's first season aired April 18.