Canon have said that they will release an update for the 5D MKII next year so that it can be switched to 24 and 25 frames per second as well as the current 30 fps. This will make it easier to convert to different system standards and is good news, their statement can be seen here:
http://www.dpreview.com/news/0910/09102003eos5dfirmware.asp
However, dont wait for the new firmware, if you are in the field and think there may be a salable sequence in front of you then go ahead and capture it.
Stephen