I have had the camera for nearly two weeks now. I do shoot Full HD at 24p almost every time I use my camera (indoors and outdoors). I have not encountered any such issues so far. Of course I don't have the need to shoot for 10 or 20 minutes at one go.
Get a P&S or borrow a friend's/family member's camera for the holiday. By the time you come came the new camera would be out and you would have no regrets about not waiting a little longer.
I have used the same grip (BG-E3) but on the even older brother - 350D, for the past two years, with one Canon original and one 3rd party battery, without any problems...
http://www.youtube.com/watch?v=QjG--kWz-L0
Video found in You Tube. It's in Japanese. But seems like shots taken at ISO6400 exhibit "very little" noise...