In an "Ask Me Anything" Session that started yesterday on reddit. Danielle Panabaker ("THE FLASH", "SKY HIGH") seemed to have confirmed that her character will infact become Killer Frost in "The Flash". With her saying that "She can't wait to suit up and duke it out with the boys". In the sessions she also confirmed that the Killer Frost costume is complete. Prehaps Killer Frost will be the main villian of The Flash's 2nd season ?
This also goes well with the rumors about the Flash's finale that state that (SPOILERS, DUH !) Ronnie dies and this lead Catlin to become Killer Frost. How she gains her powers is still unclear.