Canonrumors.com has posted a rumor that I've also had confirmed from another source.
Part of canonrumors' post is (I highly suggest you read the whole thing – didn't think it was fair to just copy all of their text):
“The 5D MarkII will have 24p, it is already in a firmware running in testing.Â It was not released due to time but it was planned to be released with the manual control.”
Thru another source, I've also heard that there's a version of the firmware that has 24p included.
Please read the whole post over on canonrumors