Unless you're into the system to begin with, a lack of enthusiasm is completely understandable.
A very expensive camera, with what will inevitably come with relatively expensive and very few lens choices to boot.
Getting excited over gear that has no relevance to me is a regular occurrence, and I suspect that many others exist with similar philosophies.
D4 I could get excited over .. and this depends on the final specs of the impending D800, but if the specs of the D800 end up on a tangent to what I want to see in my next camera, the excitement of the D4 may turn into action!
For a comparison to the ISO6400 image link you posted, here's one from a D7000 at ISO 12800:
Up to this point I had no experience with the D7000. This particular shot was captured via a friend's D7000(I don't own one) and is the 5th image I shot with it.
Does it compare favourably with the ISO6400 image from the X-Pro1?