Although the EOS-1 DX has been available to pre-order in the UK, that's not been the case in the US as dealers have had to wait for the pricing. However, the delay is over at least for customers of B&H Photo. Adorama and Amazon are sure to follow, and we'll update this post when that happens.
Pre-order the EOS 1DX body at B&H Photo ($6,799.00)
UPDATE: Adorama has been taking pre-orders for the EOS-1 DX from before Christmas, so they tell me (thanks, Helen). Please follow the link here ($6,799).