FF D400 next september

Think about this:

D800 for max resolution at 36MP with outstanding quality for the resolution at $3,000

D400 at 7 fps (8 with grip) at 24 with same Exmor Sony quality that throw the 5dmIII under the gound at $2,000-2,200 with better DR, High ISO performance, at much lower price points.

You want resolution buy D800
you want speed buy D400

D400 will not match D4 ISO performance but will be close, at 7-8fps is not going to compete with D4 for olympics & Sports in any way.
D800 will be a big step up on resolution so no direct competition.
the D400 FX will drive the sales of FX lens, more expensive. more $$ for Nikon.

If you can pay $2,000 for a body, for sure you can buy a $1,000 lens that will last years of service.