Had the opportunity to play with the MK3 today at a pre-release presentation from Canon NZ
It is AMAZING. I'm going to need to spend hours reading the manual, it's that big of a step up from the MK2. Wasn't allowed to put a card in it, but combined with the new 24-70II, the focus in low light was staggeringly good (couldn't figure out how to enable the single point in the moments I had it, so couldn't test outer points).
Official pricing for NZ is out tomorrow, and the rep confirmed release in NZ will be next week! Sooo excited, and will be pre-ordering tomorrow as soon as the retailers get their prices up.
Also, it was confirmed that the 1DX will be able to focus at f8 with a firmware update, however the rep couldn't confirm ths for the 5D.