So, Apple have released an update to the Pro Video Formats available in quicktime. http://support.apple.com/kb/DL1396?viewlocale=en_US&locale=en_US
The main thrust of this update appears to be to include MXF support in quicktime, including native support for XAVC in FCP7 and Quicktime7! I honestly never thought this would happen so I’m somewhat surprised by this. But it’s good news for FCP7 users and XAVC shooters in general. It does beg the question now as to whether you need the ProRes options for the FS7 or F5/F55.
Using Quicktime Player 7 you can play back XAVC MXF’s on a Mac computer, even in 4K, so VLC may no longer be required and the playback is smooth even with 4K clips. I’m not sure why but Quicktime Player 10 does not recognise 4K XAVC clips at all and HD XAVC clips get transcoded to .mov first. So download and install QT Player 7 for XAVC playback.
Currently it looks like the support is mainly for XAVC-I.