It´s not going to happen...
Mark Guggenheim, co-writer , explained to MTV that it was a brief appearance of Superman, but it was only in the draft...
Later, the character was vanished because of budgetary reasons...
So...
This is an excerpt from the interview:
"Without trying very hard, you could probably find the leaked script on the internet," he laughed. "[The Superman cameo] is in the leaked script. It survived several drafts. Ultimately, it was cut for budgetary reasons. We took it out in one of our later drafts"
"The Clark Kent cameo is still near and dear to my heart. I really wanted it to be in the movie," he added, only to joke, "You never know — it can still happen. If Tom Welling has a free hour or two, you never know."
