Well, you shave your head and play an evil guy and suddenly the world wants you to be Lex Luthor. Granted, if these rumors about Bryan Cranston were circulating after Malcom in the Middle and before Breaking Bad, the same people that love this idea would laugh you out of the room.
Could it happen? Sure, I guess anything could happen, but these latest rumors are all coming from the same place. AMC Movie-News' John Campea tweeted that he had heard from two unreliable sources that WB was moving forward with Cranston as Lex. Then Amasian News (a member of which happens to be his wife and which can no longer be linked because it's not up anymore) ran it as confirmed news.
Campea even took to his Facebook to tell people to chill out. You would think that these sites and writers with big followings would realize that people will run with stuff they post, but it doesn't seem to be sinking in.
And personally, I hope they don't cast Cranston because it would be a huge mistake. The same mistake they make with every Lex Luthor. "He just has to be some evil businessman, so let's get some well known older actor." No. Lex is a man in his prime, full of charisma, a man that physically looks like he can stand toe-to-toe with Superman if not for his alien biology. And with Batman/Bruce Wayne in the movie, probably working with or against Lex at some point, they should cast Lex right this time.
In continuing with our mission to keep the ship true while sailing through these rumor infested waters:
The Facts so Far on Man of Steel 2
• Henry Cavill and Amy Adams will return for the sequel (along with Diane Lane and Lawrence FIshburne), Snyder is returning to direct.
And that's really it so far. News about The Rock's deal with WB is not connected to Man of Steel 2 yet, and news about the Luthor character being in the movie is probably accurate but not officially confirmed. If you want to look at all the crazy rumors floating around about this movie so far, just take a look at the rundown here.