Conflicting news re: King Shark has come out on whether he’ll actually be appearing in the crossover event. CBR claims that in face King Shark would not be appearing in the Arrow / The Flash crossover event. It was David Ramsey, the actor who plays Diggle on Arrow, more than hinted at the synopsis involving King Shark:
[W]e are going to be tracking down a particular member of the Suicide Squad that so happens to be a 14-foot shark
But to be fair he did say the team would be on the hunt for the humanoid shark, not that they would find him or if he’d be present.
Only time’ll tell we guess. In any case if King Shark does appear again on the CW, it’d be one hell of a crossover event to remember.