Take this news with a grain of salt, but according to Comic Book Movie, Krona will make an appearance in the upcoming Green Lantern movie alongside Parallax. According to the set report
Several streets will be completely closed off to allow room for an Earth-based scene involving the fear entity Parallax and Krona.
Born on Maltus, Krona is an Oan scientist who became obsessed with observing the origins of the universe itself, despite an ancient legend that said discovering that secret would cause a great calamity. Krona constructs a machine that pierces the temporal barrier and views the beginnings of time itself. Krona catches a glimpse of the hand of creation depositing the speck that would become the entire cosmos. His machine explodes at that instant, and the universe is shattered causing the creation of the Multiverse as the universe replicates into an infinite number of parallel universes. At this same moment, the Anti-Matter Universe is created, unleashing evil into the cosmos; thus, the Monitor and the Anti-Monitor are born. As punishment for this act, Krona is transformed into pure energy by his fellow Oans and is sent to forever wander the cosmos. Krona’s actions are what caused the Oans to become the Guardians of the Universe.
If DC is really setting up a multiverse, or even hinting at it, it would certainly explain all the various incarnations of the superheroes we’ve seen the movies to date. Heck, if the Justice League movie is still in development, we may see a Crisis story building for the big super hero movie get together.
For now, this is a rumor, but at least it won’t catch you completely by surprise if it turns out to be true.