In 2008, Matthew Vaughn and Mark Miller pitched the idea of a Superman Trilogy in 2008. Even though the idea did not see the light of day, some of the ideas might have made its way to Man of Steel 2.
It has been rumored for quite a while that X-Men: First Class director Matthew Vaughn will be directing the sequel of 'Man of Steel'. Even though the rumors were confirmed by the director in 2017, the plan has fallen through and he's not attached to the project now. But, in a recent event, Vaughn has revealed his plans for Man of Steel 2, which would have lifted from a trilogy that was proposed by Vaughn and Mark Miller in 2008.
As reported by Polygon, Vaughn said that in the first movie, he proposed the idea of a trilogy that was meant to take place almost entirely on Krypton and focus on Jor-El and the impending explosion of Krypton. Even though the alien planet would still face complete destruction, in Vaughn's and Miller's movie, the event would take place in a much later timeline and it would allow Superman to grow up in his home planet and gradually become familiar with Earth. Later on, he will grow up and reckon with his loyalty to both the planets.
Even though Vaughn claims that 'Man of Steel 2' is not happening anytime soon in the near future, he revealed that he would still direct a DC Extended Universe film if asked as he finds it really hard to say no to that offer. Presently, it is unclear when Superman will appear again in the DCEU, but there are reports that actor Henry Cavil will not play the role of Superman anymore, but there are a few indications that it might not be true.
The approach of Miller and Vaughn is a quite interesting one, but there is a chance that the movie would not have worked out so well if Superman was made more alien. Along with it, it would also eliminate the chance of Clark Kent being raised as a baby, which is what makes Superman human and gives him his values like truth, justice, and the American way.
It is yet unknown what is the fate of 'Man of Steel 2' or if it is being directed by another director and the fate of Henry Cavill as Superman is still being questioned. Even though there have been numerous reports that Henry Cavil has hung his cape, both Warner Bros. and Cavill's manager have stated Cavill still owns the cape. Right now, the best guess is that Superman is being placed on the backburner while WB tries to get things right.