B&H has changed the status of the Canon EOS 5Ds and 5Ds R to read, "Item will be available for purchase on Mon, Mar 23 12AM".
That means midnight between Sunday and Monday, you should be able to preorder the highest resolution full-frame camera ever produced in whichever flavor you prefer.
Keep in mind – this site depends on support received from purchases you make using the links on our site. Please to navigate to B&H using our links once the preorders go live:
Preorder the Canon EOS 5Ds
Preorder the Canon EOS 5Ds R
Update: For those in the UK, it looks like the cameras are already available for preorder from Wex Photographic:
Canon EOS 5Ds at Wex Photographic
Canon EOS 5Ds R at Wex Photographic