The reality is, that D3s owners are more likely to change over than most think. It's only likely to cost about £1800 to swop.
For that we get a new body under warranty that is updated. A few improvements also.
In the real scheme of photography equpment, £1800 isn't a huge amount. Whenever new kit is announced, you always get people slagging off the manufacturers for not doing this, or doing that.
No such thing as the perfect bit of kit that everyone will like. That's life. You can say that about anything.
But, the D4 will sell, because it will be an excellent piece of engineering and do it's job reliably.
Will I buy one? probably. I'll enjoy discovering the new features, just as I did with the D3s
Depends how long they keep me waiting though. Not good at waiting.
Kev.