My first Nikon experience was the D7k, and I was very unsatisfied with the AF and metering...
Here's my wishlist for the D400:
DX - 18-24mp or FX 24mp with 12mp DX mode
Native iso 100-12800 with D4 auto iso features (FL info)
1080p @24/30 and 720p @60
In camera HDR with alignment (hell even my cellphone has that)
Full CLS features
Hybrid AF similiar to V1, allowing fulltime (fast) AF during video recording.