At the press conference at a London hotel on Thursday, Nikon UK's presentation mentioned the D4's autofocus compatibility with various lens combinations. From this slide it appears the D4 has 11 line sensors (most likely vertical rather than horizontal) and one cross (horizontal and vertical) sensor which are sensitive to f/8.
Canon has been widely criticized over the recently announced rival EOS-1DX, which has a 61-point AF sensor but with none more sensitive than f/5.6, to the displeasure of bird photographers. Canon say every point is vertical line sensitive at f/5.6 or greater (faster), which is very impressive but it negates AF with any f/4 or f/5.6 telephoto lenses used in-conjunction with a 2x converter. It appears Nikon has listened to this specific request, but it remains to be seen just how effective it is in real world use. It's also possible that Canon are being very conservative, this is common on pro level equipment.
Nikon don't have a super-tele at f/5.6 in the range now, but I still think we'll see a limited quantity of these in time for the Olympics in London - it won't allow AF with a 2x converter but will likely work fine with the TC-14E II.
Slide courtesy of Nikon UK.
UPDATE: UK retailer Jessops is taking pre-orders for the new D4 at £4,799.95 (inc VAT), please follow the link here.
US readers can pre-order from Adorama ($5,999.5) here.
Thank you for buying through this site's links.
Nikon announces new flagship D4